Compliance with standards

The percentage compliance with the standards in the Water Supply (Water Quality) Regulations 2018 (‘the Regulations’) is shown in Table 2 below.

Table 2. Percentage of samples meeting the standards

Parameter Group	% Compliance
Chemical Parameters	99.925
Indicator Parameters	99.979
Microbiological Parameters	99.980
Overall	99.971
Pesticides	100.00

Infographic – Compliance with the standards in 2024

Parameter name	Number of failures
Coliform bacteria (zone)	30
Coliform bacteria	14
Iron	13
Taste	8
Odour	4
Nickel	2
Colour	1
E. coli	1
Lead	1
Manganese	1
Total	75

Table 3. Number of tests carried out by companies in Wales

Company	Water treatment works	Service reservoirs	Consumer taps (zones)	Number of tests per company	Target number of tests
Albion Eco	0 (0)	0 (0)	248 (1)	248	248
Hafren Dyfrdwy	4,743 (6)	15,472 (82)	9,733 (25)	29,948	29,949
Dŵr Cymru Welsh Water	67,522 (66)	80,977 (328)	88,327 (152)	236,830	236,863
Wales overall				267,026	267,060

Numbers in brackets reflect the number of works, reservoirs or zones operated by that company in Wales in 2024. Some companies are permitted to carry out some tests on samples taken from supply points rather than from consumers’ taps and therefore the number in brackets for consumers’ taps also includes supply points.

Compliance with the testing regime set out in the Regulations, which includes limit values for contaminants in drinking water, plus frequency and location requirements, remains consistently high in Wales. This end-point verification provides broad assurance that water supply processes are delivering water to consumers that meets regulatory requirements, at the point in time the sample is taken. Water company risk assessments however, detail risks that are not optimally controlled or mitigated, and these risks, when realised, will result in water quality impact. This water quality impact may result in a compliance failure or a water quality event, both of which the Inspectorate has used to establish indices to measure companies’ ability to remediate and prevent the recurrence of the realised risk. The Inspectorate uses the compliance risk index (CRI) to measure the impact of a compliance failure, and the potential consequence of those failures on consumers. CRI is designed primarily for the purposes of effective regulation ensuring appropriate scrutiny is directed to those areas of greatest relative risk. The chart below shows company compliance risk index performance.

In 2024, CRI in Wales remains elevated in comparison to the wider industry, and there remains no discernible trend in the aggregate score. There therefore remains scope for significant improvement to strategic risk reduction approaches by Welsh companies. Targeting the largest contributors to this score would cause focus on failures at works including coliforms, turbidity, coliform failures at service reservoirs and taste and iron failures in zones. The three largest scoring compliance failures were a coliform detection at Dŵr Cymru Welsh Water’s Bretton works and taste and odour detections in Hafren Dyfrdwy’s Saltney zone. These three breaches accounted for 20% of the CRI for Wales. In 2024, Dŵr Cymru Welsh Water is the seventh highest scoring in the industry at 4.28 and Hafren Dyfrdwy sits in 18^th place at 1.10.

In total in Wales, there were two coliform breaches at treatment works and 12 coliform breaches at service reservoirs in 2024, with 11 of these breaches covered by a Dŵr Cymru Welsh Water legal instrument, which increased the CRI accordingly. The maintenance, replacement, and enhancement of key assets are fundamental to driving improvements for Dŵr Cymru Welsh Water and must remain at the core of the company’s strategic business planning. However, asset strategy is a medium- to long-term initiative with financial interdependencies. As a result of this and the increased regulatory scrutiny that comes with the company being in transformation, the CRI in Wales is expected to remain elevated in the near future. This does not mean that the quality of drinking water in Wales is anything less than excellent. Rather, long-term strategic improvements are essential to securing the supply for future generations and mitigating future risks.

Figure 2 shows variability in CRI rather than any particular trend for both Dŵr Cymru Welsh Water and Hafren Dyfrdwy, since 2020.

Figure 2. CRI scores for companies in Wales

	ALE	DWR	HDC
2020	0	4.166	0.08
2021	0	9.774	0.164
2022	0	5.397	0.563
2023	0	7.736	0.112
2024	0	4.281	1.099

Figure 3 shows the CRI for each company operating in England and Wales divided into site types; water treatment works, supply points, service reservoirs and zones (consumer taps).

Figure 3. Industry Compliance Risk Index

	Code	Reservoirs	Supply Points	Treatment Works	Zones	Total	Industry_CRI	Deadband
9		1.136612	3.711243	18.36686	1.518482	24.7332	5.195499	2
12		0.198094	0	8.595837	2.1881	10.98203	5.195499	2
18		0.084783	0.024186	9.193363	1.017916	10.32025	5.195499	2
21		0.261167	0.266739	7.792319	1.971218	10.29144	5.195499	2
17		0.018776	0	7.310596	0.571839	7.901211	5.195499	2
1		0	0	0	5.200267	5.200267	5.195499	2
5	DWR	0.41071	0	0.42015	3.450246	4.281106	5.195499	2
23		0.339677	0	2.452792	1.356032	4.148501	5.195499	2
16		0.032485	0	2.00338	1.782503	3.818368	5.195499	2
3		0.461992	0.162912	0.645375	1.565027	2.835306	5.195499	2
2		0.448877	0	0.77115	0.91107	2.131097	5.195499	2
11		0	0	0	2.131043	2.131043	5.195499	2
20		0.343347	0.227761	0.766291	0.747635	2.085034	5.195499	2
4		1.056489	0	0.390485	3.38E-05	1.447007	5.195499	2
0		0.767877	0	0	0.673067	1.440944	5.195499	2
22		0.134037	0	0.539187	0.634403	1.307628	5.195499	2
19		0.081961	0	0.685573	0.418403	1.185937	5.195499	2
7	HDC	0.150206	0	0	0.948557	1.098763	5.195499	2
15		0.291179	0	0.028044	0.76775	1.086973	5.195499	2
13		0	0	0.450692	9.58E-06	0.450701	5.195499	2
10		0	0	0	0.316083	0.316083	5.195499	2
6		0	0	0	0.211881	0.211881	5.195499	2
8		0	0	0	0.147563	0.147563	5.195499	2
14		0	0	0	4.8E-05	4.8E-05	5.195499	2

The compliance risk index (CRI) is not a statutory measure and does not override a company’s duty to comply with each parametric value outlined in the Regulations. However, as a risk-based metric, its purpose is to direct companies’ resources toward the highest risks in a precautionary manner. The CRI is shared with the financial regulator, Ofwat, as a common performance measure within an integrated regulatory strategy aimed at enhancing water quality in the public interest. A CRI target of 2 has been established as the threshold for financial penalties, ensuring that outcomes remain both achievable and equitable when used as a water quality performance objective.

The median value for the industry in 2024 is 1.77 which is a decrease from 2.322 in 2023 then 1.365 in 2022 and 1.171 in 2021. The interpretation of the median CRI for the industry can be complex because it combines two-factors; the performance by companies, and the regulatory action by the Inspectorate since the issuing of notices in response to risk amplifies the measure. Dŵr Cymru Welsh Water remains in the top half of companies with a trend which reflects the ongoing strategic risks and the increase in regulatory action.

In 2024, the CRI for companies wholly or mainly in Wales was 4.08. This is an improvement from 2023 when the figure was 7.257, then in 2022, and 5.957 after improving on 9.173 from 2021 (Figure 2). The overall CRI figure is comprised of figures representing performance at different parts of the water supply chain (treatment works, supply points, service reservoirs and zones).

Figure 4. Wales Compliance Risk Index for 2024

CRI is shown as a vertical bar for all companies in Wales, divided into zones, treatment works, and service reservoirs. The Wales industry average is shown as a single horizontal line at 3.76 and the industry target is shown as a single horizontal line at 2. Welsh Water exceed the Wales industry average and target at 4.28. Hafren Dyfrdwy are below the industry target at 1.10. Albion Eco’s score is zero.

The largest proportion of CRI is from failures in zones, which means at consumers’ taps.

Considering individual company performance; there was deterioration in the CRI figure of Dŵr Cymru Welsh Water from, 5.397 in 2022 to 7.736 in 2023 with an improvement this year to 4.28. Hafren Dyfrdwy improved from 0.563 in 2022 to 0.112 in 2023 then deteriorated to 1.10 in 2024. Dŵr Cymru Welsh Water contributed to a significant proportion of the Wales CRI figure, and also exceeded the Welsh national CRI, 4.08. CRI permits the unpacking of the key contributors to each element within the score to understand where the risks are arising, and these can be seen in Figure 4. The data includes all regulatory failures, including Indicator parameters taken at treatment works, service reservoirs and consumer taps, and is used for the CRI calculation.

Figure 5. Wales CRI score by parameter

Parameter	Reservoirs	Treatment Works	Zones	Total	Percentage	Label
A022 – Iron (total)	0	0	2.003998	2.003998	37.96	A022 – Iron (total) – 38.0%
A004 – Taste (quantitative)	0	0	1.212624	1.212624	22.97	A004 – Taste (quantitative) – 23.0%
C001 – Total coliforms (confirmed)	0.560916	0.42015	0	0.981066	18.59	C001 – Total coliforms (confirmed) – 18.6%
A003 – Odour	0	0	0.514192	0.514192	9.74	A003 – Odour – 9.7%
A023 – Manganese (total)	0	0	0.305545	0.305545	5.79	A023 – Manganese (total) – 5.8%
C001A – Coliform bacteria (indicator)	0	0	0.258686	0.258686	4.9	C001A – Coliform bacteria (indicator) – 4.9%

In Wales, breaches at large works supplying a high number of consumers continue to make up a large part of the CRI score for each year, with Bretton works in 2024, Felindre works in 2023, Ponsticill works in 2022, and Felindre works and Court Farm works in 2021. The consequence of non-compliance at large works is considered a higher risk by virtue of the number of consumers supplied. Coliforms are an indicator parameter which require action by the company as a precautionary measure to ensure the continuing protection of consumers. In the case of Bretton works, the company conducted a thorough investigation including a Water Supply (Water Fittings) Regulations 1999 inspection, treatment performance assessment and external tank inspection, however, as the contact tank is a single compartment, and can only be removed the next highest risk is not being able to take tanks of out supply for sufficient time to inspect, remediate and test before being brought back into supply.

Iron contributed to much less of the overall CRI score in 2024 at 7% compared with the previous year when it contributed to 33% of the score. However, for Dŵr Cymru Welsh Water, there were only two less failures in 2024 compared with the previous year, and 50% of the failing zones in 2024 had also failed in 2023. It is therefore not possible to conclude that benefits from short, medium and long-term strategies to mitigate and reduce these risks are being realised. Further detail on discolouration is included later in this report.

In total there were 14 microbiological breaches (no E. coli) at treatment works and service reservoirs in Wales in 2024. This is a decrease in detections from 2023 which saw 19 breaches. To maintain the high quality of Wales’ water supply, continuous risk identification is essential. Proactive measures such as tank removal and inspection, alongside regular maintenance and strategic investment, are strongly encouraged to ensure long-term sustainability.

Learning from compliance failures

Microbiological failures

In the spring of 2024 single coliforms were detected in final water samples taken at the Dŵr Cymru Welsh Water Builth and Bretton works. In both cases no definitive root causes were identified following reactive investigations. The contact tanks at both sites are single compartment tanks and resource constraints at the time prevented the timely reactive draining of these tanks for internal inspections. Pending these activities, remotely operated vehicle (ROV) inspections were conducted. Baffling in the Builth works contact tank prevented a survey of the whole tank. These examples demonstrate the need for access design and redundancy for all components that make up disinfection systems to allow for timely proactive and reactive maintenance.

Table 4. Microbiological tests – The number of tests performed and the number of tests not meeting the standard

Treatment works

Parameter	Current standard	Total number of tests	Number of tests not meeting the standard	Number of tests not meeting the standard by company
Clostridium perfringens (sulphite-reducing clostridia) (confirmed)	number/100 mL	600	0	–
E. coli (confirmed)	number/100 mL	12,108	0	–
Turbidity – indicator	NTU	12,093	0	–
Total coliforms (confirmed)	number/100 mL	12,108	2	DWR (2)

Turbidity – indicator is a critical control parameter for water treatment and disinfection.

Service reservoirs

Parameter	Current standard	Total number of tests	Number of tests not meeting the standard	Number of tests not meeting the standard by company
E. coli (confirmed)	number/100 mL	20,057	0	–
Total coliforms (confirmed)	number/100 mL	20,057	12	DWR (10) HDC (2)

Consumers’ taps

Parameter	Current standard	Total number of tests	Number of tests not meeting the standard	Number of tests not meeting the standard by company
Coliform bacteria (indicator)	number/100 mL	8,703	30	DWR (26) HDC (4)
E. coli (confirmed)	number/100 mL	8,703	1	DWR (1)
Enterococci (confirmed)	number/100 mL	753	0	–

Microbiological detections at works and service reservoirs

Table 5. Detection of E. coli and Enterococci at treatment works, service reservoirs and consumers’ taps

Company	E. coli in water leaving treatment works	E. coli in water leaving service reservoirs	E. coli at consumers’ taps	Enterococci at consumers’ taps
ALE	0 – 0	0 – 0	0 – 12	0 – 4
DWR	0 – 11,166	0 – 16,189	1 – 8,067	0 – 638
HDC	0 – 942	0 – 3,868	0 – 624	0 – 111

Note: Results are shown as the number of positive tests – the total number of tests

Service reservoirs and treated water tanks analysis

In December 2023, Dŵr Cymru Welsh Water reported two coliforms in a regulatory sample taken at Croesor service reservoir. As part of the company’s investigation, it removed the reservoir from supply in January 2024 and carried out an internal inspection. Ingress was identified through an upstand during the flood test, and the company concluded that this was the likely cause of the coliform failure. The inspection also found that the internal upstands, walls, and floor were in poor condition and required full refurbishment. The reservoir was to remain out of supply until these remedial works had been completed, and satisfactory flood testing and commissioning sampling conducted.

The Inspectorate noted that the reservoir’s return to service was twice delayed due to pH exceedances in commissioning samples, although the cause and any investigation into it, was not explained by the company until the Inspectorate questioned it. The company initially attributed the high pH results in February 2024 (pH 9.7 and 9.3) to residual product in the newly lined reservoir. A further commissioning sample taken in March again failed due to high pH (pH 10.0). At this point the reservoir was internally inspected, and it was established that the cementitious product (initially unnamed), used to reline the walls of the reservoir had not cured properly. Only on request did the Inspectorate establish the product name and its regulation 31 reference. Documentation to evidence that the product was applied in accordance with its instructions for use (IFU) were requested. It was recommended that in future the company proactively provide more robust information in a timely manner (for the reasons given below), the company did not commit to improvements and as a result received a poor response score. Companies should be aware of the importance of proactively providing key information, supported by evidence, as soon as possible during an Inspectorate assessment. A piecemeal approach, responding only when prompted, may raise concerns about intentional concealment and can unnecessarily prolong the assessment process. In this case, the lack of transparency further diminished confidence in a company already under increased scrutiny due to its ongoing transformation.

Failure of a company (or its contractor) to apply or introduce a substance or product in accordance with regulation 31(1) is an offence under regulation 33(3)(a), although it is not an offence if the water that is exposed to the product is not supplied for consumption. In this case, no potential offence was committed as the reservoir was not in supply. The commissioning samples of the water acted to mitigate a near miss, illustrating how important the recommissioning process is in protecting consumers.

The Inspectorate concluded that whilst there was no absolute evidence that the contactor followed the IFU at the time the material was being applied to the interior reservoir walls, the steps of the procedure had been recorded (albeit lacking in detail). The critical question remained as to why the material did not cure as it should have done if the IFU was indeed followed, which the company claimed was the case. To address this, the company initiated an investigation while suspending the product from use for internal coatings until further notice.

Croesor service reservoir remained out of service while refurbishment of the walls was completed using an alternative regulation 31 approved product. It should be noted that the highest pH result returned on a commissioning sample at this reservoir (pH >10) was taken in April following this recoating with the second product. This demonstrates that potential pH issues following the application of cementitious coatings is not limited to an individual product, rather cement-based products more generally.

When cementitious products are tested for use in contact with water intended for human consumption (BS 6920) the testing is preceded by initial soaking periods. These soaking periods act to draw out the compounds in cement which are liable to leach out and raise the pH of the water in contact with the cement. In this case the company investigation concluded that the elevated pH detected was due to a combination of aggressive feed water (when compared to the water used to test the product according to BS 6920) and a greater surface area to volume ratio in the reservoir compared to test conditions. Hence, companies should consider the surface area to volume ratio when applying coatings to the internal parts of tanks, and the initial tendency for cementitious products to raise the pH of water in contact with the product.

The company, following prompting from the Inspectorate, undertook an internal audit to ensure that their contractors have procedures in place to ensure regulation 31 approved products are used in accordance with manufacturers’ instructions. A further technical review by a third-party consultancy which included queries over the curing time and the surface area to volume ratio was also conducted.

In conclusion, the company’s commissioning procedure following the application of both cementitious products was able to both prevent water with a high pH from going into supply. In addition, the curing issues experienced with the first product were only identified once the service reservoir had been drained down after high pH results. Companies are reminded to state the reason for any delay in the return-to-service of an asset and to include an evidence-based investigation for any parameter breach of a commissioning sample as part of its ongoing reporting duties. Companies are also reminded that they are ultimately responsible for work conducted by contractors on their behalf, and the record keeping and communication between the company and contractors may be called upon following a potential breach of the Regulations. Regular scheduled company audits of their contractors should reveal potential deficiencies in contractor procedures, processes and record keeping.

Figure 6. Compliance breaches at Dŵr Cymru Welsh Water service reservoirs and treatment works

Year	Reservoirs	Treatment Works
2016	6	1
2017	2	1
2018	3	3
2019	5	1
2020	7	2
2021	15	5
2022	3	3
2023	13	3
2024	10	2

There have been 12 bacteriological compliance failures at Dŵr Cymru Welsh Water works and service reservoirs in Wales in 2024. The majority of the breaches were associated with ingress into service reservoirs. While this is an improvement on the previous year, the company is yet to fully realise the benefits of the service reservoir work delivered against its regulation 28 notice since it was served in April 2022. To fully realise the benefits, the company must establish a suitable base-level of inspection and maintenance, based on risk, to achieve and maintain an overall reduction in risk.

On 30 October 2024 a compliance sample was taken by Dŵr Cymru Welsh Water at Newlands service reservoir which contained one total coliform per 100 mL. The ingress of roots (Image 1: below, top left) and a worm (Image 2: below, top right) through the gaps in the wall to roof joints was identified during a reactive internal inspection of compartment one on 13 November 2024, which is a brickwork tank with an aluminium roof (Image 3: below), with no defects identified in compartment 2 which is of a concrete construction. These defects in compartment 1 were concluded as the most likely root cause for the breach. Similar observations of leaking roof joints during flood testing were made during an internal inspection of compartment 1 in September 2020. Whilst repairs were carried out and the tank reinspected with a passing flood test in November 2020 the microbiological compliance breach in October 2024 demonstrates the importance of risk assessment in defining appropriate maintenance programmes. Where the construction, condition and relative risks associated with separate assets on a single site varies this should also be considered when designing these programmes.

Images 1, 2 and 3 Newlands service reservoir

A sample taken by Hafren Dyfrdwy at Cefn Twlch service reservoir on 5 April 2024 contained a single coliform per 100 mL. The reactive investigation highlighted defects with the sampling facilities including a poor sampling environment, with the tap housed in a roadside cabinet with overhanging trees, and inadequate drainage. The tapping point chamber was also found to be flooded providing opportunity for ingress. The company stated that the sampling facilities did not conform to the existing design standards, and in response, installed a new sampling kiosk prior to the return of the reservoir to supply and initiated additional annual reservoir sample facility audits to be conducted by local operatives. Companies are reminded that sampling facilities should meet the requirements of regulation 16 with respect to ensuring appropriate, hygienic sampling facilities are available for obtaining representative compliance samples. Such facilities should conform to companies’ own standards and deviation from said standards should be noted and remediated following observation through routine site visits, inspections and other risk assessment processes.

Figure 7. Number of microbiological breaches in Wales zones

Year	DWR	HDC
2016	7	NULL
2017	10	NULL
2018	6	3
2019	13	6
2020	9	1
2021	10	1
2022	17	4
2023	20	4
2024	27	4

In Figure 7, while the lower figures in 2020 and 2021 can largely be attributed to reduced sampling during the pandemic, the overall trend has continued to rise year on year since 2018. Of the 31 breaches recorded in 2024, 26 were deemed unlikely to recur, with 20 of these linked to the domestic distribution system.

This upward trend may be influenced by the replacement of older taps with simple spouts by modern designs incorporating additional internal features, such as aerators, which can promote microbial growth. Swabbing taps before sampling could help identify them as potential sources of contamination.

For the remaining five breaches, the cause was not determined. However, company responses have continued to improve, and it is positive to note that no recommendations were issued for these breaches in 2024.

Chemical and physical parameters

Table 6. The number of tests performed and the number of tests not meeting the standard

Parameter	Units	Total number of tests	Number of tests not meeting the standard	Number of tests not meeting the standard per company
Colour	mg/L Pt/Co	3,187	1	HDC(1)
Odour	Dilution number at 25°C	3,183	4	DWR(3) HDC(1)
Taste (quantitative)	Dilution number at 25°C	3,183	8	DWR(7) HDC(1)
Hydrogen ion (pH) – indicator – zone	pH Value	3,186	0
Sulphate	mg/L SO₄	462	0
Sodium (total)	mg/L Na	755	0
Nitrate (total)	mg/L NO₃	756	0
Nitrite – consumers taps	mg/L NO₂	755	0
Ammonium (zone)	mg/L NH₄	921	0
Aluminium (total)	µg/L Al	3,152	0
Iron (total)	µg/L Fe	3,155	13	DWR(12) HDC(1)
Manganese (total)	µg/L Mn	3,156	1	DWR(1)
Copper (total)	mg/L Cu	755	0
Fluoride (total)	mg/L F	462	0
Arsenic (total)	µg/L As	755	0
Cadmium (total)	µg/L Cd	754	0
Cyanide (total)	µg/L CN	462	0
Chromium (total)	µg/L Cr	755	0
Mercury (total)	µg/L Hg	465	0
Nickel (total)	µg/L Ni	755	2	DWR(1) HDC(1)
Lead (10)	µg/L Pb	755	1	DWR(1)
Antimony	µg/L Sb	755	0
Selenium (total)	µg/L Se	755	0
Pesticides (total by calculation)	µg/L	704	0
Polycyclic aromatic hydrocarbons (total by calculation)	µg/L	727	0
Residual disinfectant – free	mg/L	8,746	0
Residual disinfectant – total	mg/L	8,121	0
Electrical conductivity	µS/cm at 20°C	2,959	0
Boron	mg/L B	455	0
Benzo[a]Pyrene (total)	µg/L	761	0
Tetrachloromethane (total)	µg/L	464	0
Trichloroethene & Tetrachloroethene – sum of 2 substances (total by calculation)	µg/L	465	0
Trihalomethanes (total by calculation)	µg/L	757	0
1,2-Dichloroethane (total)	µg/L	466	0
Benzene (total)	µg/L	466	0
Bromate	µg/L BrO₃	583	0
Gross alpha	Bq/L	1	0
Gross beta	Bq/L	1	0
Tritium	Bq/L	1	0

Lead

Lead is a toxic metal that can dissolve into drinking water when it comes into contact with lead pipes. Consumers are largely protected from exposure through phosphate dosing, a widely used treatment across many zones in Wales that reduces plumbosolvency. This approach is one of the key reasons why few, if any, consumer tap samples fail the lead standard each year. Additionally, the relatively low number of required lead tests under the Regulations contributes to this outcome.

As part of Price Review 2024, companies submitted lead reduction strategies with a target of achieving lead-free water supply zones by 2050. However, current plans will not meet this goal, therefore there is an expectation that strategies will accelerate in subsequent AMPs.

The single failure in the Wales area in 2024 was attributed to a lead communication pipe within a phosphate dosed zone. This pipe was replaced with MDPE and the consumer was given flushing advice due to lead solder on their private plumbing.

Taste and odour

There were 12 taste and odour breaches in Wales in 2024 which is an increase from 10 in 2023 which can be seen in Figure 8. In Dŵr Cymru Welsh Water’s Bontgoch zone, an investigation is being undertaken by Atkins Realis in response to a building history of taste and odour failures. It also experienced three taste cancellations, one of which was due to particulates present in the sample in relation to a burst main event, another being due to discolouration which required further investigation to prove as transient. Figure 8 also highlights a rise in failures in 2019 following the introduction of Information Letter 02/2022, which mandated companies to report cancelled taste tests as failures. The number of failures declined in 2020 and 2021, attributed to adjustments in sampling locations during the pandemic. Whilst the last three years have similar numbers of taste and odour failures, the taste and odour section further on in this report describes an increasing rate of contacts regarding taste and odour across Wales across the past few years.

Figure 8. Taste and odour breaches in zones (including breaches located in England)

ReturnYear	Odour	Taste
2016	3	2
2017	7	2
2018	10	3
2019	12	11
2020	2	NULL
2021	5	2
2022	3	8
2023	3	7
2024	4	8

In June 2024 Dŵr Cymru Welsh Water cancelled taste analysis on a sample following the detection of a spider in the sample bottle (Images 4 and 5 below). This follows a similar occurrence in October 2023, in which a fruit fly was found in a sample bottle. In both cases the company reported the taste cancellation as a regulatory compliance breach as required by Information Letter 02/2022. A recommendation was made for the company to review and update their sampling and bottle storage policy/procedures to mitigate the potential for the ingress of insects during sampling, with the company implementing additional contamination checks as a result.

Images 4 and 5 Spider in sample bottle

Iron

Dŵr Cymru Welsh Water is optimising treatment processes at Talybont works for multiple drivers, one of which is the apparent increase in algal activity in the supplying reservoir. One failure in the Abergavenny zone was attributed to this issue. There is a rolling GAC regeneration programme due for completion at the end of 2025 which should improve removal efficacy for taste and odour compounds. Improvements at Talybont works are formalised in a regulation 28 notice.

Figure 9. Dŵr Cymru Welsh Water iron breaches

Year	DWR
2018	14
2019	15
2020	7
2021	7
2022	21
2023	14
2024	12

Distribution iron breaches continue across Wales with these discussed in 10 assessment letters during 2024. Given the association with the ongoing poor performance in other discolouration metrics in Wales this trend is a cause for concern. In some cases, the existing legal instruments in place have provided assurance that network interventions will mitigate recurrence in the short term. However, a large number of breaches were associated with the impact of mains in poor condition, local flow dynamics and other legacy conditions which have been mitigated through reactive flushing programmes. The impact of these programmes has in some cases proved detrimental rather than beneficial to local water quality and recommendations have been made to ensure appropriate monitoring and control of this impact. In some instances, flushing has been conducted prior to reactive/investigatory sampling and so investigations into root causes have been compromised. The trailing of Welsh companies behind industry targets suggests that current investment and delivery of agreed projects is not delivering the required changes at a sufficient pace.

In January 2024, a sample taken in a Hafren Dyfrdwy concessionary supply zone breached the regulatory standard for colour. Properties in this zone are supplied by individual private sources and are subject to a permanent boil water notice (BWN). A regulation 28(4) notice was served on 8 November 2023 which requires all properties in this zone to be connected to the mains water network by 31 March 2026. The BWN is unlikely to mitigate the risk from wholesomeness aesthetic breaches such as colour. A recommendation was therefore made that precautionary do-not-drink advice be issued following breaches of non-microbiological parameters in the concessionary supplies zone.

There were two nickel failures in Wales in 2024. Both were attributed to new chrome taps, however the failure in Hafren Dyfrdwy’s legacy zone was from a sample taken from a little-used utility room tap. A suggestion was made to review the tap selection procedure to ensure that samples taken are representative of the incoming supply.

Learning from events

Water quality events infographic

Figure 10 shows the highest scoring events in 2024. A small number of these event assessments are ongoing, therefore the assessment conclusions are estimated.

Figure 10. Highest Event Risk Index

Events	ERI Score
HDC – Saltney Taste & Odour	240.065
DWR – Talybont Water Treatment Works Taste and Odour	94.471
DWR – Tynywaun Water Treatment WorksTurbidity	57.096
DWR – Glascoed Taste and Odour	16.664
HDC – Newtown Lead Do Not Drink	15.03
DWR – Llanrumney Burst Main	5.972
DWR – Gilfach Fargoed Loss of Supply	4.599
DWR – Rhydlafar Burst Main	2.737
DWR – Abergavenny 3rd Party Damage	2.5
DWR – Pengarnddu Old Service Reservoir	2.09

Most events notified to the Inspectorate in 2024 were of short duration with 45 of the 57 lasting less than 72 hours. Four of the top scoring events had a duration of greater than 200 hours which is more than eight days. The highest scoring event in 2023 was Dŵr Cymru Welsh Water’s Penyball works chlorate event, followed closely by a second chlorate event and its Penycefn works. These scored 12.294 and 8.096 respectively. In 2024, the top scoring event was Hafren Dyfrdwy’s Saltney taste and odour event with a score of 240.065. There are five events in 2024 scoring higher than the highest scoring event of 2023. The higher scores will have been caused by one or more of the ERI variables which include the seriousness score, assessment score and impact (population affected multiplied by duration of event). Figure 11 shows ERI for Wales in 2024.

Figure 11. Wales ERI and median ERI

	ReturnYear	CompanyCode	ERIAll	Median	Wales	Region
0	2024	HDC	255.4426	187.9788	192.298	192.298
1	2024	DWR	187.9788	187.9788	192.298	192.298
2	2023	ALE	0	187.9788	192.298	192.298

A common theme in 2024 was network failures with associated consumer impact of loss of supply and/or discolouration in the Dŵr Cymru Welsh Water area. To minimise the impact of the loss of supply, the company employs alternative supplies commonly in the form of tankering, to infuse into the network or to fill service reservoirs. These activities have attracted recommendations regarding sampling requirements, particularly that tanker must be sampled at the point they discharge into the network.

Table 7. Top 10 scoring events notified in 2024

Company	Event name	Cause of event	Final event assessment	ERI score
HDC	Saltney Taste & Odour	Treatment failure upstream of final disinfection	4	240.065
DWR	Talybont WTW Taste and Odour	Raw water deterioration	4	94.471
DWR	Tynywaun WTW Turbidity	Structural failure – Treatment works	4	57.096
DWR	Glascoed Taste and Odour	Raw water deterioration	3	16.664
HDC	Newtown Lead Do Not Drink	Company communication pipe problem	4	15.03
DWR	Llanrumney Burst Main	Mains problem/ damage – Mains – Burst	3	5.972
DWR	Gilfach Fargoed Loss of Supply	Mains problem/ damage – Mains – Burst	4	4.599
DWR	Rhydlafar Burst Main	Mains problem/ damage – Mains – Burst	4	2.737
DWR	Abergavenny 3rd Party Damage	Mains problem/ damage – Mains – Damage by Third Party/Unknown	4	2.5
DWR	Pengarnddu Old SRV	Animacules	1	2.09

Gilfach Fargoed Loss of Supply

A large-scale loss of supply event occurred following a burst on the inlet main to the Gilfach Fargoed service reservoir serving the Treharris area of South Wales. Company contractors were working in the area at the time to expose a section of the local wastewater network. During this excavation, the 24-inch cast iron main feeding Gilfach Fargoed service reservoir was damaged, resulting in a downstream loss of supply (Image 6 below).There were an associated 373 loss of supply and 105 discolouration contacts. The company repaired the main and conducted survey sampling, hydraulic modelling, rezoning, alternative supply and flushing operations to monitor and mitigate the impact on consumers. The event highlights the importance of understanding and mitigating the risks posed by planned excavations to critical underground supply infrastructure. It also serves to demonstrate the importance of contractor supervision and auditing to provide assurance of compliance with defined water quality and sufficiency risk mitigation processes during works.

Image 6 Fractured 24 inch main

Glascoed Taste and Odour

A taste and odour event occurred in May 2024 which was associated with the breakthrough of 2- methyl isoborneol (MIB) at Glascoed works. There are no dedicated granular activated carbon (GAC) adsorbers on site, but this media is incorporated into the site’s CoCoDAFF system. The company initiated powdered activated carbon (PAC) dosing and raw and treated water reconfiguration initiatives to eliminate and/or dilute MIB concentrations and flushing to mitigate the impact on consumers. A total of 14 consumer contacts were received in relation to the event. The taste and odour concentration triggers for operational interventions and investigation following detections at various process points were reviewed by the company and a new site-specific action plan was created. The reduction in taste and odour removal efficiency through the overloading of the granular activated carbon within the site’s CoCoDAFF system with coagulant floc, was identified as a contributing factor. The provision of acid dosing to facilitate a reduction in coagulant dose is planned to address this. The event highlights the importance of taste and odour compound treatment capacity provision and management. It also demonstrates the requirement to intervene with appropriate operational actions, such as the initiation of PAC dosing, at the earliest opportunity following apprehension of taste and odour contacts and/or compound concentration elevation.

Rhydlafar Burst Main

A burst on an 18-inch cast iron main on the outlet of Radyr service reservoir in Cardiff associated with damage caused by ground movement after heavy rain led to loss of supply and discolouration impacting 4,723 consumer properties on 18 October 2024. Rezoning and alternative supply operations were conducted to restore supplies. Elevated metals were detected in several survey samples including a tanker filling point and seven samples taken from active tankers which were taken out of service in response. Companies are encouraged to refer to the requirements of regulation 6 and consider the impact of such operations on both tanker and local up/downstream network water quality at the tanker filling and infusion points.

Barry Do Not Drink

A consumer contact from Barry Leisure Centre in February 2024, reported a strong chemical odour and reports of illness from consumers. The company issued precautionary do not drink advice on the day of apprehension, in response. On investigation during a Water Supply (Water Fittings) Regulations 1999 inspection (fittings inspection) on the same day and subsequent sampling surveys, contamination with corrosion inhibitors via a cross connection to the site’s heating system was identified. The company issued a Water Industry Act 1991 (the Act) section 75 notice to remediate the plumbing defects prior to resampling and rescinding of the do not drink notice. Companies are reminded of their duty under regulation 21 to pursue investigatory and enforcement actions, where appropriate, to prevent the recurrence of water fittings contraventions which have resulted in the supply of unwholesome water within a public building. This includes recurrence of water fittings contraventions at the property in question as well as at other buildings where work has been or could be conducted, for example where a third-party contractor is responsible for plumbing work across multiple public buildings. All instances of offences, offence investigations and decision making regarding the pursuance or otherwise of prosecution should be recorded in company systems.

Tynywaun Turbidity

At the end of November 2024, the South Wales valleys experienced a significant period of rainfall during Storm Bert with the equivalent of one month’s rainfall falling in Treherbert within a 48-hour period between 22 and 24 November 2024. The rain gauge at Tynywaun works, which feeds the Treherbert area, registered 172 mm of rain during this period. Over the course of the evening of 23 November 2024 the final water turbidity at Tynywaun began to rise and then exceeded 1 NTU whilst all upstream water quality trends were satisfactory. The site was running at a reduced disinfection stage capacity due to a compartment of the distribution cum contact tank being out of supply for inspection at the time. The operators identified a leak into the live contact tank compartment via a damaged joint and a decision was made to issue boil water notices to 28,525 consumers in the downstream zone. Subsequent sample surveys proved satisfactory in terms of microbiological compliance, including Cryptosporidium sampling from the works to consumers properties. Whilst timely electronic communications were made, the working time restrictions of the contracted courier company meant that the boil water notices were delivered to consumers two to three days after this decision was made. This advice continued until remedial works were completed on the out-of-supply contact tank compartment, it was returned to supply and continuing satisfactory sample results were obtained. The company did not include analyses for certain schedule 1 parameters such as hydrocarbons and pesticides in survey sampling based on a catchment occurrence risk assessment. Where surface water ingress into treated water holding structures is suspected or confirmed companies are encouraged to verify any associated risk assessments for schedule 1 parameters through appropriate reactive sampling. This event also highlights the importance of careful contingency planning to inform timely interventions in the event of the failure of stand-alone disinfection process assets. It also demonstrates the importance of regular inspection and maintenance activity to assure the integrity of disinfection and treated water holding assets.

Abergavenny boil water notices

During an investigatory response to a consumer water quality contact from the Forest Coal Pit area near Abergavenny, reactive samples from local properties indicated widespread microbiological contamination. A series of boil water notices were issued in response to these results. A mixture of supply arrangements were identified with properties variously on dedicated private supplies, a combination of public and private supplies (both live and disconnected) and public supply only. The properties on public supply were fed from a historic large bore outlet main for an upstream works that had been decommissioned in 2003. Flow, turn-over, free chlorine and pressures in the area from the now reversed flow supply, were low. The upstream decommissioned works had been isolated by valving in 2003, but a connected 1.4 km stagnant section of main was left at a higher elevation than the properties in question, creating the potential for pressure head. Leaks were identified on this stagnant main and an air gap was installed immediately downstream of the last property on the system to isolate this section of main from supply during the response to this event. The company has not been able to prove a definitive root cause for the event and has taken steps to improve local network turn-over and free chlorine. The investigation into this event demonstrates the importance of planning the decommissioning of supply assets to ensure that risks to local network water quality are not introduced.

Saltney taste and odour

Following a contamination event on a tributary of the River Dee the compound 2-isopropyl-3-methoxypyrazine broke through treatment at the receiving Severn Trent works. This led to a downstream taste and odour event in both the English and Welsh water quality zones in Chester. The consumer contact event reporting trigger for a hydraulically connected area was reached in the combined bulk supply fed Hafren Dyfrdwy and upstream Severn Trent water quality zone but notification of an event to the relevant authorities was raised for the Severn Trent area only. This breach of the requirements of regulation 35(6) resulted in a warning letter being issued to the company to prevent recurrence. Companies are reminded that, to comply with the requirements of regulation 35, water quality events which occur, or are likely to occur, on both sides of a bulk supply boundary should both be reported to the relevant authorities. The association with the upstream event should also be detailed in the event notification text for the bulk supplied area. Further details of this event that affected three water companies are in the taste and odour section of this report.

Newtown Lead

On 12 April 2024, Hafren Dyfrdwy took a lead investigatory sample at a consumer tap, with pre- and post-flush results of 688 µg/L and 20.21 µg/L, respectively. As the post-flush results were above 10 µg/L, the company responded by issuing do not drink advice to four properties on a shared supply whilst the lead services on both sides of the property boundary were replaced and satisfactory resamples taken.

However, the company had previously sampled this property in July and August 2022, at the request of the consumer. In August 2022, the pre-flush lead result was 4,885 µg/L, almost five hundred times greater than the lead standard of 10 µg/L. A filtered aliquot of this sample, and the flushed result were both below 10 µg/L. Flushing advice was issued in response with a single letter to each property on the shared supply; properties were not sampled again or subject to a supply pipe investigation until April 2024. Furthermore, during the investigation it was found that the water quality zone in which these properties were located had been rezoned to a supply which was not phosphate dosed. Phosphate dosing was listed as a control measure for lead in the company’s risk assessment. This rezoning had taken place prior to the sampling in 2022 and was not reversed until November 2023 and represented a significant period during which this control was absent. Companies are reminded that lead concentrations should be measured as total lead. A warning letter was sent to the company with further sanctions considered in case of repeat events of this nature.

Llanrumney Burst Main

In February 2024, a burst main occurred on Dŵr Cymru Welsh Water’s 15-inch trunk main supplying several areas of Cardiff. Initially, supply was lost to over 10,000 properties, however, the company was able to restore or maintain a piped supply to 4,095 of these properties by rezoning and to a further 1,187 properties by use of tankers. Seventeen tankers were deployed during the event, and issues were identified with the company’s compliance with regulation 6, with two demountable tankers not sampled at the commencement of distribution and instead sampled the following day, with one of these samples breaching the prescribed concentration for iron.

The burst point was located within 5 metres of a watercourse, the main was repaired and recharged. The company received 12 calls regarding water quality over two days, seven of which reported discoloured water. The company also received 146 contacts reporting no water.

Abergavenny third-party-damage

In April 2024 significant damage to an air valve on a high pressure 12 inch trunk main feeding the town of Abergavenny was caused by agricultural ploughing equipment being used in a field near the town. The air valve pipework was sheared at the tee connection to the trunk main causing catastrophic failure (Images 7 and 8 below). This led to a significant loss of supply and discolouration event across the downstream Abergavenny area. The company isolated and repaired the damaged assets, provided alternative supplies and conducted survey sampling to monitor and mitigate the impact on consumers. The scouring effect of the event on the local network led to short-lived elevations in manganese in downstream assets and properties. The company has a regulation 28(4) notice in place at the upstream Talybont works to improve manganese removal and has network flushing programmes for sediment removal. A Talybont trunk main conditioning program is also planned following completion of manganese removal improvements at the works. These elevations in manganese highlight the importance of viewing risks to water quality in terms of the entirety of the supply system, from catchment to consumer, to enable informed interventions at critical points to maximise benefit. The air valve in question was not classed as a critical valve and so was not subject to routine inspections. Companies are encouraged to ensure inspection, servicing, risk assessment and mitigation actions relating to air valves, including assessing the risk of potential damage caused by third parties, on critical trunk mains such as this are completed on a regular basis.

Images 7 and 8 Valve damaged in field

Pengarnddu Old Service Reservoir

Dŵr Cymru Welsh Water’s Pengarnddu Old service reservoir is a single compartment tank, constructed in 1915 and is a critical asset to supply water to the Merthyr Tydfil area. Originally an open tank, a roof was added around 40-50 years ago. There is no record of this tank ever having been drained down and inspected and the company has been unable to remove the tank from supply to complete this work, since this would impact supplies downstream. This service reservoir had single coliform breaches reported in both December 2021 and November 2023, both of which were not fully investigated since the tank could not be isolated or internally inspected. In 2018, the Inspectorate served a notice (DWR-2018-00002) to the company to build a new service reservoir asset to supply the Merthyr Tydfil area, and this work was completed in 2023. In 2022, the Inspectorate served a notice (DWR-2021-00002) to inspect all service reservoirs and tanks which had not been inspected in the previous 10 years, and this included Pengarnddu Old service reservoir. In September 2023, the new service reservoir, Pengarnddu no. 3, was brought into commission, allowing enabling works to begin on Pengarnddu Old service reservoir so that it could be removed from supply without impacting consumers. The tank was successfully removed from supply in June 2024, drained and a full internal inspection undertaken.

When completing the internal inspection, a large amount of debris was noted on the floor of the tank (Images 9, 10, 11 and 12 below), and when inspected, skeletal remains of an animal were discovered embedded within this sediment.

Images 9, 10, 11 and 12 Debris in service reservoir

This was therefore reported to the Inspectorate as a water quality event. Since the tank had already been isolated, any risk posed to the general public had already been removed at that point. The remains were analysed in the laboratory and found to be that of a domestic dog. From the condition of these remains, it was thought that this had been in situ for a prolonged period (Images 13 and 14 below).

Images 13 and 14 Skeletal remains of a dog

Due to the extensive remediation required to bring this tank up to a satisfactory standard, this work is still ongoing, and this asset remains out of supply.

This case highlights the importance of regular inspection and maintenance of service reservoirs and tanks, including maintaining the ability to remove these assets from supply when necessary. Companies should regularly review their supply arrangements to ensure that changes to demand are accounted for in their risk assessments and in planning for inspections.

Morriston Do Not Drink

In June 2024, a Dŵr Cymru Welsh Water consumer reported a “sewage” and “foul” taste and odour in their supply. A company inspector attended the property the same day and noted an odour, but did not describe it as “sewage”; liaison with a water quality scientist did not take place and precautionary restriction of use advice was not issued at this time. Samples were taken the following day with results showing presumptive Clostridium perfringens present, and a do not drink notice was issued, two days after the initial call. A subsequent company water fittings inspection found a dead squirrel in the consumer’s uncovered hot water cistern (Image 15 below), at this point a do not use notice was issued which remained in place until remedial works had been completed.

Image 15 Squirrel in hot water tank

St Asaph Do Not Drink

In September 2024, a consumer in St Asaph, Denbighshire, contacted Dŵr Cymru Welsh Water to report a petrol like odour to their drinking water. An investigation was carried out by the company which identified elevated concentrations of hydrocarbon compounds, indicative of polycyclic aromatic hydrocarbon (PAH) contamination in the supply to the complaining property and one neighbouring property. The supply from other neighbouring properties on the same main was satisfactory.

PAH contamination of the water supply is rare, and when it does occur, is normally found to be caused by coal tar lining of iron water mains, accompanied by very low flow. In this case however, the source was identified as likely to be from a treated telegraph pole located in the vicinity of the supply pipes to the two affected properties and similarly treated railway sleepers used in planters on the grass verge outside of the two properties. Soil samples from around these sources confirmed contamination with similar PAH compounds (Images 16 and 17). A small section of blue plastic communications pipe connected the properties to the main ran near to the telegraph pole and underneath the planters and this has now been replaced. The rest of the supply pipe was found to be made from barrier pipe. During the investigation, both properties were given a restriction of use notice until the section of plastic pipe had been replaced, and satisfactory samples had been obtained.

Images 16 and 17 Excavation of communication pipe and main and planters constructed with railway sleepers on grass verge.

The company had previously received a similar complaint in 2020 from the same property, however the investigation carried out at the time did not correctly identify the cause and the investigation was closed prematurely, leaving the consumer at risk of drinking unwholesome water. Since then, the company has accepted an undertaking from the Inspectorate, for regulation 18 Investigations (DWR 2022-00002), and following this, a regulation 28(4) notice (DWR 2024-00007), also for regulation 18 investigations. The procedure for investigating petrol type taste and odour complaints has been reviewed and updated, thus the investigation in 2024 was significantly more comprehensive and robust, allowing the company to identify and resolve the issue for the consumers.

Consumer contacts

Acceptability of water

The acceptability of drinking water was ranked by consumers as their top priority and can be affected by several factors including its appearance, for example, discolouration or aeration, or the taste and/or odour. Most acceptability complaints are caused by a black, brown, or orange discoloration of water which are caused by raised concentrations of manganese, iron, and aluminium.

Whilst these metals are rarely at a concentration which is harmful to health, they can and do cause widespread rejection of water based upon appearance. The expectation and priority of a consumer is for their water to be clean and safe, and therefore, events which cause discolouration are highly disruptive to consumers with the inevitable drop in confidence which follows. The Inspectorate takes these events very seriously and many companies have regulation 28(4) notices in place to focus on the root causes of discolouration. In February 2024, the Inspectorate issued Information Letter 01-2024 Annual Provision of Information on Consumer Contacts, which set out new requirements for companies to report a greater level of detail on their consumer contacts which included the following additional requirements:

A unique reference for each contact;
Details of the district metered area the contact is located in;
The date and time of the contact;
The national grid reference (easting and northing) of the location of the contact;
The mode of contact;
Whether the contact is a repeat within a 12-month rolling period (that is a new occurrence or ‘case’ of a similar issue from the same consumer);
and if the contact is associated with a notifiable event, and the event reference number associated with it.

Information regarding multiple contacts, for example if a consumer reports more than one drinking water quality concern during a contact, is also recorded.

The data submitted from companies in 2025, covering 2024 is the first submission to include this additional data, therefore direct year on year comparisons for the new data is not yet possible. To maintain continuation of a comparable data set and monitor industry performance and progress, only primary contacts and no event contacts have been used in the reporting of acceptability data for 2024.

In Wales in 2024 there were 9,950 consumer contacts regarding acceptability of drinking water, reported to companies wholly or mainly in Wales. This is a rate of 3.02 per 1,000 population. Table 8 shows the number of contacts received for each type of complaint for Welsh companies, with contacts relating to discoloured water (brown, orange, black) being the most common reason.

Table 8. Water quality complaints in Wales, 2024

Category	Contacts
Appearance – Brown Black Orange	5,624
Taste / Odour – Other	741
Appearance – White Air	733
Taste / Odour – Chlorine	533
Drinking water quality concern – Lead and Analysis	504
Illness – Gastroenteritis	377
Appearance – Particles	314
DWQ Concern – Incident Related	311
Appearance – General Conditions	209
Taste Odour – Earthy Musty	209
Appearance – White Chalk	134
Illness – Skin	76
Appearance – Blue Green	66
Illness – Oral	34
Taste / Odour – Petrol Diesel	28
Illness – Medical Opinion	26
Appearance – Animalcules	18
Drinking water quality concern – Lifestyle	9
Drinking water quality concern – Pets Animals	4
Drinking water quality concern – Campaign	0

Discoloured water

The Inspectorate reviews consumer contact data for discoloured water contacts on an annual basis. Companies whose performance is poorer than the industry average are investigated, and enforcement action taken where necessary. Dŵr Cymru Welsh Water has had a company-wide notice in place since 2022, with six individual zonal notices remaining from AMP7. Companywide discolouration performance is considered when serving notices, in addition to individual water supply zone performance. When completed, these legal instruments will improve water quality to consumers supplied in these areas.

The number of contacts reporting discoloured water (brown, orange or black) across the industry (England and Wales) over recent years has been decreasing, however 2024 has seen a slight deterioration on the previous year’s performance (Figure 12). In Wales, the rate was also relatively stable, but has also seen a deterioration in 2024, from 1.58 contacts per 1,000 population in 2023 to 1.70 contacts per 1,000 population in 2024.

Figure 12 Welsh company and industry discolouration rates 2015 to 2024

Year	Appearance – Brown black orange Rate, for Wales	Industry average
2015	2.14	0.78
2016	2.30	0.79
2017	2.14	0.72
2018	2.26	0.70
2019	1.83	0.62
2020	1.77	0.61
2021	1.54	0.54
2022	1.59	0.50
2023	1.58	0.47
2024	1.70	0.49

The chart shows the industry average discolouration rate (for contacts per 1000 population) for the past 10 years (between 2014 and 2023). The Industry has made a steady improvement over the years, from 0.85 contacts per 1000 population in 2014, to 0.47 contacts per 1000 population in 2023. The picture in Wales is somewhat worse, although still improving, from 2.33 in 2014 to 1.58 in 2023.

The 2024 rate of 1.7 per 1000 population in 2024 in Wales is significantly higher than the industry average of 0.49. Of those Welsh contacts, 98.56% are from consumers served by Dŵr Cymru Welsh Water, who remain the worst performing company in the industry for discolouration (Figure 13).

Figure 13 Rate of discolouration contacts by company in 2024 (excluding Isles of Scilly and inset companies)

The graph shows the discolouration rate for companies in England and Wales in 2024. Dŵr Cymru Welsh Water has the highest rate and is the worst performer in the industry. Hafren Dyfrdwy remains below the industry average and sits in 11th place.

Company	Company Discolouration Rate 2024	Industry Average
	2.79	0.49
DWR	1.80	0.49
	1.27	0.49
	0.69	0.49
	0.57	0.49
	0.57	0.49
	0.51	0.49
	0.45	0.49
	0.44	0.49
	0.43	0.49
	0.43	0.49
HDC	0.38	0.49
	0.34	0.49
	0.25	0.49
	0.15	0.49
	0.14	0.49
	0.12	0.49
	0.10	0.49
	0.07	0.49
Industry Average	0.49

Wales Average	1.70

Figure 13 shows where the Welsh companies rank over the whole industry for discolouration contact performance in 2024.

The contact rate for Hafren Dyfrdwy, which had been showing an improvement, has stalled in recent years (Figure 14). The company’s rate remains under the industry average.

Figure 14 Rate of discolouration contacts for Hafren Dyfrdwy (per 1,000 population)

Hafren Dyfrdwy Discolouration Contact Rate per 1,000 population. The discolouration contact rate for Hafren Dyfrdwy shows an overall improvement from 0.61 in 2020 to 0.38 in 2024.

Year	Appearance – Brown black orange Rate	Industry
2020	0.61	0.60
2021	0.68	0.54
2022	0.41	0.50
2023	0.36	0.47
2024	0.38	0.49

Figure 15 Rate of discolouration contacts for Dŵr Cymru Welsh Water (per 1,000 population)

Dŵr Cymru Welsh Water Discolouration Contact Rate per 1,000 population

Year	Appearance – Brown black orange rate	Industry
2020	1.85	0.60
2021	1.60	0.54
2022	1.67	0.50
2023	1.66	0.47
2024	1.80	0.49

Dŵr Cymru Welsh Water remain an industry outlier and have seen a deterioration in performance in 2024. Dŵr Cymru Welsh Water had a number of zone-specific discolouration notices and a companywide notice for discolouration. Three of the zone-specific notices have been delayed into AMP8. The company-wide notice was served in 2022 with a target of 1.4 contacts per 1,000 population to be achieved by the end of AMP7. Figure 15 shows that the company fell short of this target. When there was an early indication that this target would not be met, the Inspectorate engaged with the company to better understand why the company believed this was the case by critically evaluating how the company determined its deliverables and the resulting impact. Part of this ongoing notice included setting a new target for the end of AMP8 using the same methodology as that for the AMP7 target. The company’s new target is 1.08 contacts per 1,000 population.

Taste and odour

Similar to discoloured water contacts, the rate for total taste and odour contacts for the industry has gradually reduced year on year, although in 2024 this rate has worsened, to 0.25 per 1,000 population. In Wales, the rate is almost double the industry, at 0.46 in 2024 and is seen to be gradually increasing, from 0.36 in 2022.

Figure 16 Rate of taste and odour contacts in Wales

Year	Taste / Odour Chlorine Rate	Taste / Odour Earthy Musty Rate	Taste / Odour Other Rate	Taste / Odour Petrol Diesel Rate	Taste / Odour Total Rate	Industry Rate for taste and odour contacts (all categories)
2020	0.17	0.05	0.24	0.01	0.46	0.26
2021	0.17	0.05	0.22	0.01	0.45	0.25
2022	0.13	0.04	0.18	0.01	0.36	0.22
2023	0.13	0.04	0.19	0.01	0.37	0.22
2024	0.16	0.06	0.22	0.01	0.46	0.25

The River Dee contamination event, which led to Hafren Dyfrdwy receiving a warning letter, also impacted United Utilities and Severn Trent Water at upstream locations. The source of the contamination was traced to a self-service milkshake bar on a farm, where an inadequate drainage system allowed 2-isopropyl-3-methoxypyrazine (IPMP) to enter the river.

Since IPMP is a food-grade compound, it did not activate the ‘Deepol’ system, leaving the responsibility of investigation and sampling to the abstracting water companies. The Inspectorate was notified of the contamination through the water quality event notification process.

United Utilities customers experienced the greatest impact, with the company receiving 968 consumer complaints between 5 and 31 August 2024, 786 of which were related to taste and odour issues. Learning from these events in England can be found in Drinking Water 2024 England.

Events contacts

With the additional consumer contact information available to the Inspectorate for 2024, the number and category of event-related contacts have been reviewed. Although these contacts do not feed into the contact rates for each company or the industry as a whole, they provide valuable insight into the location and volume of these reports. Understanding these patterns helps identify potential hotspots and background levels of contacts, enabling improved oversight.

In Wales, there were six events which generated discoloured water contacts, as can been seen in Figure 17. Two of these events, Gilfach Fargoed loss of supply and Abergavenny third party damage, are amongst the top 10 events in the industry for discoloured water contacts.

Figure 17 – 2024 Discolouration events in Wales by number of consumer contacts

Event Name	Discoloured BrownBlackOrange	Discoloured BlueGreen	Particles	WhiteAir	WhiteChalk	EarthyMusty	PetrolDiesel	Other tasteorodour	Gastroenteritis	Skin	contacts
DWR Llwynypia Quarry Loss of Supply	3										3
HDC Newtown T&O	2							1			3
HDC Saltney Taste & Odour						3		3	1		7
DWR Llanrumney Burst Main	9			2			2	1			14
DWR Abergavenny 3rd Party Damage	78		2	5				2		1	88
DWR Gilfach Fargoed Loss of Supply	100	2	4	22	11			3	2		144

Asset health

Treated water tanks and service reservoirs

The Inspectorate remains committed to strengthening the integrity of service reservoirs and treated water tanks. In 2024, this initiative has included comprehensive audits of service reservoirs and ongoing scrutiny of the regulation 28(4) notices issued to both Welsh companies in 2022.

For Dŵr Cymru Welsh Water in particular, the impact of this notice is now fully evident. As of April 2025, all service reservoirs and treated water tanks have been removed from supply to enable a full drain down and inspection, with now none that are in service, exceeding 10 years between inspections. Some of the inspections are outstanding, however the Inspectorate expects these to be completed before these tanks are returned to supply, as part of the regulation 28(4) notice obligations. Dŵr Cymru Welsh Water should be commended for the efforts made to complete this important work to ensure every tank has undergone a full assessment within the past decade.

Figure 18 shows the good progress made by Dŵr Cymru Welsh Water, with no tanks in supply that have not been inspected within the past 10 years.

Figure 18 Dŵr Cymru Welsh Water tank inspections

Year	Total number of service reservoirs	Total number of service reservoirs at risk	Percentage of service reservoirs at risk	Label
2022	711	41	5.8	5.8% 41 Tanks
2023	704	45	6.4	6.4% 45 Tanks
2024	697	32	4.6	4.6% 32 Tanks
2025	696	0	0	0% 0 Tanks

Figure 19 shows the progress made by Hafren Dyfrdwy. There are seven ‘at risk’ tanks which have not been fully inspected in the past 10 years, marginally more than in 2023. Three of these tanks are covered by separate regulation 28(4) notices and require a new tank to be constructed to enable the existing tanks to be removed from service. A short term measure in these notices is to conduct remotely operated vehicle inspections to provide information on current internal tank condition and integrity .

Figure 19 Hafren Dyfrdwy tank inspections

Year	Total number of service reservoirs	Total number of service reservoirs at risk	Percentage of service reservoirs at risk	Label
2022	118	15	12.6	12.6% 15 Tanks
2023	118	11	9.2	9.2% 11 Tanks
2024	118	5	4.2	4.2% 5 Tanks
2025	118	7	5.9	5.9% 7 Tanks

Figure 20 Industry – tank assets at risk

The number of tanks is represented by a vertical bar for each company in England and Wales. A horizonal line shows the percentage of at risk tanks. The companies are in the order of percentage tanks at risk. The highest on the left and the lowest on the right.

Hafren Dyfrdwy has the 4th highest percentage of at risk tanks in England and Wales.

Granular activated carbon management

There have been several events in 2024 involving the breakthrough of taste and odour compounds at Glascoed and Talybont works as well as at an upstream works in Chester impacting a bulk supply into the Saltney water quality zone. In each case the management of taste and odour treatment, namely granular activated carbon adsorbers (GAC) and powdered activated carbon (PAC) dosing systems, has played a role in this breakthrough. Recommendations have been made to companies in response to audits and event assessments to address shortcomings in contemporary and historic GAC management practices. The contemporary adsorbance capacity of the GAC at works will define their ability to remove most taste and odour compounds where they are installed to mitigate taste and odour risks . This adsorbance capacity is impacted by several factors including the loading experienced at the site over time, the frequency at which the media has been historically regenerated and the length of time that the process water is in contact with the carbon. A common theme in the taste and odour events in Wales in recent years, is the failure of companies to appreciate the existing status of GAC adsorbance capacity, until the point at which it becomes overwhelmed by a rapidly developing raw water challenge. Examples include high solids loading, low adsorber media iodine numbers associated with excessive run-times between media regeneration, and a failure to adequately monitor and control empty bed contact times. A carefully planned and routine monitoring and intervention strategy for adsorbance capacity, contact time and associated adsorber performance metrics is therefore important in mitigating the recurrence of such events.

In addition to conventional GAC adsorbers, another option to increase a sites carbon adsorbance capacity is the dosing of powdered activated carbon (PAC) into the process stream. In several instances this operational intervention has not been effective in mitigating breakthrough of taste and odour compounds during events. In some cases operational triggers have not enabled a timely enough response. In other cases, insufficient dosing capacity or contact time have limited the effectiveness of the dosed PAC. Companies are trialling different PAC products in an effort to improve contaminant removal at identical contact times and the sharing of information between companies regarding the outcome of these trials is encouraged. The verification and optimisation of applied PAC dose through live monitoring and offline laboratory methods, for example jar testing, is also encouraged.

Disinfection control

There were several events in Wales in 2024 which involved the compromising of disinfection processes through unmitigated elevations in turbidity. The events at Tynywaun and Penybont works constituted both breaches of the requirements of regulation 26 and of company disinfection strategies. The sources of this turbidity included variously the mobilisation of sediments within, and the ingress of surface water into, disinfection process assets. The absence of appropriate risk assessments, adequate asset maintenance and redundancy, sufficient water quality monitoring equipment, run to waste facilities and sufficient network resilience all contributed to the impact of these events. Site control systems should be configured to ensure failures of disinfection processes and equipment are apprehended and controlled at the earliest opportunity. Systems to contain and dispose of undisinfected water should also be carefully considered in the design of these systems where possible. Deficiencies in the site-specific risk assessments and disinfection policies have been identified during different audits conducted in 2024. For example, the treatment performance requirements for viruses and Cryptosporidium had been assessed in some analyses but not those required for bacteria. Whilst conservative performance requirements had been applied it is important that companies assess the risks and control measures in place at works for each pathogen group listed in the Regulations.

Water safety planning and risk assessment

The Inspectorate’s Risk Assessment team’s function is to understand water companies’ water quality and sufficiency risks, adaptations to new requirements for mitigation and approaches to Drinking Water Safety Planning (DWSP). The team assesses large amounts of data and documentation submitted by companies. This information gives the Inspectorate the ability to act and enable companies to comply with regulations 27 and 28 using different types of audits including DWSP audits, individual line assessments (ILAs) of regulation 28 data, and legal instrument closure audits. By making assessments of all the above, the team can progress and maintain risk management practices across the industry. The team also issues guidance where necessary to help companies in their approach to compliance with the regulations regarding risk assessment.

Drinking Water Safety Plan (DWSP) guidance

The World Health Organization (WHO) published an updated Water Safety Plan (WSP) manual in March 2023. During 2024, the Inspectorate worked on revising DWSP guidance to incorporate the approach and continuing endorsement of fundamental components described in the WHO WSP manual. A draft of the new guidance was circulated to members of Water UK’s Drinking Water Safety Plan Forum to enable companies to give feedback on changes made. The new guidance aims to improve consistency in reporting DWSP data across the industry.

The feedback from the industry included needs for general clarification on wording regarding risk scoring, supporting documents to an overarching DWSP methodology and referencing, inclusion of the hazard ‘quantity’, nitrate/nitrite formula inclusion, hazard groups, regulation 26 turbidity inclusion, PFAS and pesticide reporting requirements and future risks. A working group was convened in December, hosted by Southern Water, where clarification for company queries was documented for feedback. The specific issues regarding hazardous events and a carried forward risk recording method was concluded. The working group also concluded that an annual return of regulation 28 data was not necessary. The upload data from the Inspectorate database shows many risk lines are skipped during the annual submission due to companies reviewing risks throughout the year. Companies may still submit an annual data set if they wish but this will no longer be a requirement following an update to the Water Industry (Suppliers’ Information) Direction due to be published in 2025.

The Inspectorate added a new category J to account for carried forward risks as part of this guidance and has also mandated the application of categories regarding regulation 27 and 28 notices. Category D must be applied to risks and/or risk lines with control measures identified by any regulation 27 or regulation 28 notice within three months of receiving a notice. Category E must be applied to risk lines for assets identified within regulation 27 and regulation 28 notices or whole company notices where specific parameters or control measures have not been listed, and a review of risks is required, also to be applied within three months of receiving a notice. The Water Industry (Suppliers’ Information) Direction 2024, incorporated regulation 28 reporting specifications. This enabled better tracking of the reporting requirements for the industry and separates DWSP guidance from the requirements for provision of information.

Audits

The Inspectorate continues to highlight recurring themes across all DWSP audits undertaken to date, including the variability and inconsistency of recording of risks across the industry and a continuation of reactive rather than proactive drinking water safety planning. Companies must move towards improved DWSP processes that proactively protect public health and ensure compliance for regulatory parameters rather than only maintaining a DWSP approach in retrospect of water quality or quantity issues.

The majority of DWSP audits to date have resulted in ‘minded to enforce’ and/or legal instruments being served to review regulation 27 risk assessments and regulation 28 reporting. The new DWSP guidance should address some of the inconsistencies that have been identified throughout the year and improve the quality of the information provided.

During 2024, the risk assessment team completed four audits on the DWSPs at Portsmouth Water, Southern Water, Dŵr Cymru Welsh Water and Northumbrian Water alongside Inspectors from the regional teams within the Inspectorate.

Portsmouth Water

Following a review of the company’s regulation 27 notice, it was identified that there were outstanding actions required to comply with the requirements of the notice. The company therefore continues to work on its surface water catchment risk assessments.

Southern Water

The Risk Assessment team undertook a two-day audit which comprised a day to assess the company’s DWSP, and a day’s technical site audit at Findon water treatment works and Tenants Hill service reservoir. A number of deficiencies were identified with the DWSP, the main areas highlighted included that although there was sufficient knowledge of risks within the company, this was not always reflected in the DWSP. There was a requirement for the company to produce an overarching methodology rather than rely on several separate documents which should be referenced within the methodology. The company demonstrated a lack of proactive risk assessment resulting in the company not proactively assessing all the company risks to drinking water supplies, and a strong reliance on sample results alone to identify risks. Other areas of concern included a lack of procedure around interpretation of bulk supply incumbent risk scores.

Dŵr Cymru Welsh Water

A two-day DWSP audit including a review of disinfection policy at Bryn Cowlyd works and a site visit to Pyllau service reservoir, resulted in a regulation 27 ‘minded to enforce’ letter. Whilst the staff present at the audit appeared to have a good understanding of the technical areas within the DWSP, several recommendations were made around the company methodology. These included the requirement to include details on how bulk supplies are risk assessed, definition of the assets and stages included in the DWSP process as well as any seasonal variations in assets in service, and information on how the DWSP process is conducted, all of which are fundamental elements of a DWSP. Other areas identified as needing improvement included documenting of training and competence, descriptions for triggers for action on risk identification, and the process for assigning risk scores and DWI categories.

Northumbrian Water

The assessing Inspectorate team were joined by colleagues from the Drinking Water Quality Regulator for Scotland (DWQR) for a two-day DWSP audit and technical audit at Mosswood water treatment works and Castleside service reservoir to understand how the company are progressing in delivery of their companywide notice for Hazard Review, developing and implementing their DWSPs throughout the hazard review process and to see evidence of improvements specific to Mosswood works.

The operational staff at Mosswood works and Castleside service reservoir were found to be very knowledgeable of these sites and the company have been commended for this. However, the key findings of the audit identified unacceptable risks associated with clarifier maintenance and wash water supernatant return, both of which present the risk of turbidity impacting disinfection and efficacy of significant barriers for the removal of Cryptosporidium. The audit also found that changes to the disinfection policy were required. As such, the Inspectorate issued the company with ‘Minded to Enforce’ letters covering the required actions for delivery under legal instruments yet to be served.

Risk Assessment Record (RAR) reporting and company breakdown of DWI categories

The annual submission of companies’ regulation 28 risk assessment report data took place in October 2024. Companies were able to use the online portal for the 2024 submission including uploading of their DWSP methodologies and declaration with Director sign off. There are occasionally issues with new processes for data submissions, however problems were easily resolved with good communication from companies and input from the Inspectorate’s Data Management Unit (DMU).

Companies’ risk assessment record (RAR) data is submitted using the DWI categories shown with definitions in the table below [Table 9] Companies must apply DWI categories appropriately to allow data to be meaningful and to give clarity in risk management. The risk assessment risk index (RARI) score multiplier is included in the table below along with an indication of whether the number of days a category is in place is considered in the RARI calculation. This shows that, for hazards not yet mitigated and verified (C, D, E), the RARI score multiplier increases a companies’ RARI score for those hazards significantly, dependent on the number of days these categories are in place. See the RARI section below for company scores.

Table 9 RARI calculation

DWI Hazard Category	Description	RARI Score Multiplier	Days in Category used?
A	Target risk mitigation achieved, verified and maintained	0.1	No
B	Additional or enhanced control measures which will reduce risk are being validated	0.5	Yes
C	Additional or enhanced control measures which will reduce risk are being delivered	2	Yes
D	Additional or enhanced control measures are required to materially reduce risk	3	Yes
E	Risk under investigation	4	Yes
F	Partial mitigation	0.1	No
G	Control point downstream	Not included in the calculation
H	No mitigation in place and none required	0.1	No
I	Future risk	Not included in the calculation
J	No mitigation in place, carried forward risk: control point upstream	Not included in the calculation
X	Risk record no longer relevant	Not included in the calculation

The pie chart in Figure 21 below shows that over half of the industry identified risks to water quality have verified mitigation in place.

Figure 21 – DWI RAR categories applied across the industry – all stages

A	58.1%
B	1.98%
C	3.31%
D	4.88%
E	1.56%
F	1.26%
G	5.42%
H	22.85%
I	0.64%

Figure 22 below shows the percentage of RAR categories across the industry at the treatment stage for England and Wales.

Figure 22 Percentage RAR categories for the whole industry at the treatment stage

DWI Category	% Category at Treatment Stage
A	64.80%
B	2.50%
C	3.80%
D	7.80%
E	1.70%
G	0.20%
H	18.50%
Hazards needing mitigation and validation (B C D E)	15.80%

Risk assessment record categories F, G, I and X have been excluded from the above Figure 22. Category F accounted for 0.18% of treatment stage risks across the industry where there is partial mitigation at this stage, usually these risks are also further mitigated downstream, and companies may use category G to also represent these risks. The percentage of category G risks at treatment works was 0.2%. These risks are typically hazards such as nitrate that can be mitigated by blending downstream of the treatment stage in company distribution systems. Category I risks made up 0.8% of the total risk categories applied at the treatment stage, although the use of this category may increase as the industry expands DWSP and records future risks to water quality and sufficiency of supply. Future risks are also discussed below. Category E has been included in the data described as ‘hazards needing mitigation and validation’, however there may be risk outcomes that demonstrate mitigation is not required.

Hazards with categories C, D and E contribute to high RARI scores over time. As these categories indicate investigations into hazards (E), mitigation being needed (D), and solutions in the delivery phase (C). The longer the categories remain in place during this process, the longer there is a risk of water quality from these hazards. The top ten hazards in the section below show which hazards have the highest percentage of whole industry RARI scores. Category B risks may have had mitigation delivered, reducing the risk to water quality, however, the mitigation now in place for these risks is still being verified. Companies with regulation 27 and 28 notices must retain hazards at category B until the end of such notices, and the Inspectorate is satisfied through company completion reports that any hazards under notice have suitable control measures in place.

Risk Assessment Risk Index (RARI)

The risk assessment risk index (RARI) is dependent on DWI category application to risks perceived by companies. Companies are required to report risk assessments and show where risks are carried forward through supply systems from catchment/source to the consumer’s tap. Since the introduction of DWI categories, companies have used different methods to show carried forward risks. This is achieved either by using the DWI categories applied at assets with active risks and applying the same categories at downstream assets; or using residual risk scoring to demonstrate risks moving forward through a supply system. As such, RARI values for companies have not been comparable across the industry and can only show changes over time when viewed on an individual company risk profile. RARI has been reported for companies within the Chief Inspector’s annual reports over the last five years from 2019 to 2023. The index is a useful tool in showing active risks within companies and is being redeveloped as companies implement changes to how DWI categories are applied, gaining a more consistent approach over the next few years. This includes the introduction of a new category ‘J’ for carried forward risks. Although this category will not be included in the RARI calculations, it will allow for a more consistent approach within the industry for category application across company supply systems.

Figure 23 Top 10 current identified risks – whole industry

Hazard Name	% Whole Industry RARI
No supply	16.22%
Cryptosporidium oocysts	12.29%
Perfluorooctane Sulfonate	11.95%
Perfluorooctane Acid	11.31%
E. coli	10.76%
Enterococci	9.51%
Total coliforms	7.94%
Lead	7.04%
Clostridium perfringens	6.65%
Turbidity	6.33%

The top 10 hazards represent 39% of all hazards included in RARI calculations.

Figure 24 Top 10 industry risks in Wales

Hazard Name	%
No supply	22.11568497
Cryptosporidium oocysts	9.643718013
Turbidity	6.42746683
E. coli	5.02128647
Enterococci	4.862668372
Iron	3.982326435
Manganese	3.646189053
Clostridium Perfringens	3.137347796
Total coliforms	3.081463892
Aluminium	2.952460944

Company average RARI scores for 2023 and 2024 are shown below. The median value is 7.78.

Figure 25 Company average RARI scores 2023 and 2024

Company	2023	2024
ISC	643.51	2110.28
ESP	38.68	184.58
VWP	746.85	169.41
PRT	272.78	129.67
HDC	117.43	47.43
NES	11.77	25.20
BRL	17.66	23.56
SVT	5.22	19.22
SWB	12.72	14.94
SRN	8.88	13.16
SST	9.21	12.49
ANH	8.16	11.27
DWR	6.60	9.43
WSX	3.38	6.12
SES	0.53	4.78
CAM	4.82	4.40
YKS	2.96	4.29
TMS	1.79	4.15
SEW	3.18	3.96
UUT	3.17	2.08
LNW	1.60	1.53
AFW	0.29	0.72
IWN	0.57	0.39
ICW	0.44	0.19
ALB	0.18	0.13
ALE	0.07	0.07

Figure 26 company average RARI scores 2023 and 2024

Company	2023	2024
ISC	643.51	2110.28
ESP	38.68	184.58
VWP	746.85	169.41
PRT	272.78	129.67
HDC	117.43	47.43
NES	11.77	25.20
BRL	17.66	23.56
SVT	5.22	19.22
SWB	12.72	14.94
SRN	8.88	13.16
SST	9.21	12.49
ANH	8.16	11.27
DWR	6.60	9.43
WSX	3.38	6.12
SES	0.53	4.78
CAM	4.82	4.40
YKS	2.96	4.29
TMS	1.79	4.15
SEW	3.18	3.96
UUT	3.17	2.08
LNW	1.60	1.53
AFW	0.29	0.72
IWN	0.57	0.39
ICW	0.44	0.19
ALB	0.18	0.13
ALE	0.07	0.07

RARI scores have increased for 15 out of the 26 companies shown in the above figures between 2023 and 2024 as the industry has increased hazard identification and recording of risks. This is likely to be the case over the AMP8 period through improvements made to hazard identification processes. These improvements may be implemented through Inspectorate legal instruments served on companies and/or development of approaches in line with newly published DWSP guidance. Companies must implement changes to recording and reporting risks in line with the Water Industry (Suppliers’ Information) Direction 2025 by February 2027.

AMP7 RARI trends

The RARI trends across the AMP7 period shown below are indicative of where the Inspectorate expects companies to be. As companies continue to identify and record risks in their DWSPs, an increase in RARI scores is inevitable, as observed in 2023 and 2024. The Inspectorate expects to see company RARI scores vary over time as risk identification is improved and solutions to mitigate risks are delivered, downward trends will follow over future AMP periods as companies work through PR24 schemes and legal instruments. The rates of change in RARI scores will vary between companies as each has their approach to DWSP linking to investment plans and timescales for delivery of any control measures needed to reduce water quality risks.

Portsmouth Water and Hafren Dyfrdwy RARI trends are shown on the primary axis in the graph below (Figure 27) for scale alongside companies with similar trends.

Figure 27 Company AMP7 RARI trends

Company	2020	2021	2022	2023	2024
ISC	0	0	519.561	643.51	2110.3
ESP	0	0	190.06	38.684	184.58
VWP	0	0	101.529	746.85	169.41
PRT	9.58	13.20	31.01	272.78	129.67
HDC	39.198	72.352	124.830	117.43	47.425
NES	0.42	1.28	1.60	11.77	25.20
BRL	13.08	6.47	4.63	17.66	23.56
SVT	5.58	10.10	5.15	5.22	19.22
SWB	1.22	2.95	13.27	12.72	14.94
SRN	2.98	3.34	5.31	8.88	13.16
SST	0.75	2.78	7.41	9.21	12.49
ANH	4.00	7.85	3.23	8.16	11.27
DWR	1.533	2.015	2.864	6.6	9.434
WSX	0.48	0.54	1.82	3.38	6.12
SES	0.13	1.67	0.21	0.53	4.78
CAM	0.07	0.05	8.95	4.82	4.40
YKS	2.53	1.41	0.74	2.96	4.29
TMS	1.32	1.36	1.62	1.79	4.15
SEW	1.36	1.67	5.40	3.18	3.96
UUT	1.40	2.93	4.12	3.17	2.08
LNW	1.89	5.68	3.11	1.60	1.53
AFW	0.39	0.68	1.14	0.29	0.72
IWN	1.64	1.00	0.85	0.57	0.39
ICW	0.50	0.85	0.42	0.44	0.19
ALB	0.23	29.41	0.18	0.18	0.13
ALE	0.00	0.00	0.07	0.07	0.07

Both companies have had high RARI scores over the last few years described below.

Hafren Dyfrdwy included risks identified through notices served in 2022 to their DWSPs, including a regulation 28 notice on individual service reservoirs and affected supplied zones, and a notice for concessionary supplies and installation of large water mains to supply areas north and south Lake Vyrnwy. As the company has made good progress with delivery of solutions under these notices, this is shown by a decreasing trend in their RARI scores from the middle of AMP7 to present.

Portsmouth Water was served a regulation 27 notice for catchment risk assessment and a management and training regulation 28 notice served in 2021, leading the company to identify and record these risks in their DWSPs shown by an increase in RARI from 2022 to 2023. The company continues to be on target with delivery against these notices indicated by a decrease in their RARI scores across their supply systems from 2023 to present.

Cambridge Water and United Utilities show similar trend profiles across AMP7 with RARI scores increasing during 2021 to 2022, followed by a decline in scores to 2023 as delivery of solutions conclude during 2025 and early 2026.

Companies shown in Figures 29 and 30 below show similar increases in RARI scores at the start of AMP7 to those in Figure 28 above, however further increases have followed from 2022 to present due to other legal instruments served during the AMP period and updates to ongoing notices for AMP7 continuing into the AMP8 period. Companies with RARI scores >10 at the end of 2024 are shown in Figure 28 below.

Figure 28 Company AMP7 RARI trends

Company	2020	2021	2022	2023	2024
ISC	0	0	519.561	643.51	2110.3
ESP	0	0	190.06	38.684	184.58
VWP	0	0	101.529	746.85	169.41
PRT	9.58	13.20	31.01	272.78	129.67
HDC	39.198	72.352	124.830	117.43	47.425
NES	0.42	1.28	1.60	11.77	25.20
BRL	13.08	6.47	4.63	17.66	23.56
SVT	5.58	10.10	5.15	5.22	19.22
SWB	1.22	2.95	13.27	12.72	14.94
SRN	2.98	3.34	5.31	8.88	13.16
SST	0.75	2.78	7.41	9.21	12.49
ANH	4.00	7.85	3.23	8.16	11.27
DWR	1.533	2.015	2.864	6.6	9.434
WSX	0.48	0.54	1.82	3.38	6.12
SES	0.13	1.67	0.21	0.53	4.78
CAM	0.07	0.05	8.95	4.82	4.40
YKS	2.53	1.41	0.74	2.96	4.29
TMS	1.32	1.36	1.62	1.79	4.15
SEW	1.36	1.67	5.40	3.18	3.96
UUT	1.40	2.93	4.12	3.17	2.08
LNW	1.89	5.68	3.11	1.60	1.53
AFW	0.39	0.68	1.14	0.29	0.72
IWN	1.64	1.00	0.85	0.57	0.39
ICW	0.50	0.85	0.42	0.44	0.19
ALB	0.23	29.41	0.18	0.18	0.13
ALE	0.00	0.00	0.07	0.07	0.07

Companies with RARI scores <10 at the end of 2024 are shown in Figure 29 below.

Figure 29 Companies’ AMP7 RARI Trends (less than 10)

Company	2020	2021	2022	2023	2024
DWR	1.533	2.015	2.864	6.6	9.434
WSX	0.48	0.54	1.82	3.38	6.12
SES	0.13	1.67	0.21	0.53	4.78
CAM	0.07	0.05	8.95	4.82	4.40
YKS	2.53	1.41	0.74	2.96	4.29
TMS	1.32	1.36	1.62	1.79	4.15
SEW	1.36	1.67	5.40	3.18	3.96
UUT	1.40	2.93	4.12	3.17	2.08
ALB	0.23	29.41	0.18	0.18	0.13

NAV RARI score changes across AMP7 are shown in Figure 30 below. The figure excludes ESP Water, Veolia Water Projects and Albion Eco. Albion Eco continues to have a RARI score of 0.07 for the one site it is responsible for at Shotton Mill. ESP Water and Veolia Water Projects data are shown in the whole industry AMP7 RARI table above.

Figure 30 NAV RARI scores across AMP7

Year	LNW	IWN	ICW	ESP	VWP
2020	1.89	1.64	0.50	0	0
2021	5.68	1.00	0.85	0	0
2022	3.11	0.85	0.42	190.06	101.529
2023	1.60	0.57	0.44	38.684	746.847
2024	1.53	0.39	0.19	184.58	169.41

Future risks

Seventeen companies use category ‘I’ indicating their individual perceived future risks that may need to be investigated and mitigated. Such risks include hazards that may be associated with emerging contaminants, climate change, changes in raw water quality and sufficiency, and asset condition and longevity. These risks are not necessarily manifesting now, but companies are keeping a watching brief over them. The top ten hazards where category I has been used in company submitted regulation 28 data is shown below.

Figure 31 Top 10 whole industry future risks – England and Wales

Hazard Name	%GT Count of Hazard Name
Nitrate	7.03%
No supply	6.28%
Total coliforms	2.22%
Per- and polyfluoroalkyl substances (PFAS)	2.02%
Iron	1.79%
E. coli	1.72%
Cryptosporidium oocysts	1.49%
Turbidity – indicator	1.38%
Clostridium Perfringens	1.27%
Lead	1.25%

The Figure 32 below shows that the highest proportions of company perceived future risks are from abstraction and storage stages.

Figure 32 Percentage category I risks by supply system stage

Stage	Percentage of category I
Abstraction	39.79%
Storage	32.81%
Treatment	13.66%
Catchment	11.31%
Distribution	2.35%
Consumer	0.09%

Examples of these risks included single source contamination associated with nitrate risk, structural integrity of service reservoirs leading to a sufficiency of supply risk, and degradation of internal structures of boreholes causing a risk of iron in the raw water source supplied.

Raw water

As part of water safety planning, annual submissions of raw (untreated) water data are made to the Inspectorate. Sampling focuses on identifying hazards, assessing their presence and severity. This data plays a crucial role in guiding catchment management efforts and shaping the design, operation, enhancement and optimisation of treatment processes.

For the past century, water quality stressors have been primarily anthropogenic, with increasing freshwater demand and the polluting consequences of the urban, industrial and agriculture sectors. With climate change driving the increase in frequency and severity of extreme events such as storms and floods, inland water quality is set to continue worsening. This will further strain waste and drinking water treatment works and threaten drinking water supplies, and thus, there is a need for a more comprehensive quantification of raw water quality, to understand past and current trends through data.

In 2024, the Inspectorate commissioned a research project in association with the University of Cambridge to analyse the raw water dataset held by it to see what insights could be generated. The dataset comprises:

Around 22.1 million test results.
- 13.5 million are of groundwater samples.
- 8.4 million are of surface water samples.
764 parameters have been tested.
At 3,258 sites.

The project aims to deliver a tool which can initially be used for the interrogation of a small set of parameters to enable effective analysis with the potential to expand the number of parameters at a later stage.

A better understanding of the evolving distributions of different chemicals across water company catchments will facilitate data-driven prediction of contamination risks and potential for contaminated drinking water sources. Understanding how these contaminants behave through treatment works could enable the prevention of contamination events, enabling water suppliers to mitigate transient increases in chemical levels in the raw water. The Inspectorate has been collating raw water quality data collected by water companies since 2009 and is now extending its analysis of treated water compliance data to this growing set of raw water data. Analysis will support the Inspectorate in assessing the consequences of action or inaction in catchments and the relationship between the outputs of water safety plan risk assessments and the test results. It will also help identify hotspots and highly stressed areas that might begin to struggle to provide drinking water to regulatory standards in the future.

Poly and perfluoroalkyl substances (PFAS)

Given the increased identification of the risk of Poly- and perfluoroalkyl substances (PFAS) in UK and global waters in recent years, the Inspectorate has started reviewing this group of chemicals separately to the rest of the dataset. These are sometimes referred to as ‘forever chemicals’ and are byproducts of various industrial processes being practiced over the last 80 years. This project will facilitate a separate inspection of the PFAS subset.

The Environment Agency (EA) conducted the first extensive spatial analysis of 41 PFAS parameters in England from February to December 2023. They analysed 631 sites (275 ground water, 309 river and surface water, 47 coastal and estuarine river), and performed analysis per water source type. They identified a significant difference in PFAS detection in each raw water source, with river and surface waters having triple the detection frequency than groundwater across all measured parameters. This is likely due to the differing transport and fate dynamics, with attenuation processes in groundwater diffusing PFAS contamination. This study only pursued data collection for a spatial analysis of PFAS in England; temporal analysis has not yet been carried out for PFAS in England to date.

As of May 2025, the PFAS database has:

Around 1,789,000 test results.
- 832,000 are raw water.
- 957,000 are operational.
48 parameters.
2,275 sites.

The project continues into 2025 with the aim to complete the interactive tool focusing on the initial small number of parameters selected, with ideas around future work to expand this analysis to cover a more extensive range.

Poly and perfluoroalkyl substances (PFAS)

In August 2024, the Inspectorate updated its guidance to the industry regarding requirements to submit test results and summary risk assessment information for PFAS. Companies have continued with their targeted sampling strategy to focus on those sites which are likely to be at risk from PFAS contamination. In 2024, companies in England and Wales collectively carried out over 770,000 analyses for individual PFAS, and in total, over 1.8 million analyses have been performed since 2012, providing a significant dataset to understand the challenges in drinking water.

PFAS tiers are now applied to any PFAS chemicals of interest detected in the final or raw water. Sites are classified as:

Tier 1 where PFAS concentrations are <0.01 µg/L.
Tier 2 where PFAS concentrations are <0.1 µg/L.
Tier 3 where PFAS concentrations are ≥0.1 µg/L

PFAS tiers are to be applied to all PFAS chemicals of interest identified in the parameter list (Annex C of the Information Direction) detected in final water. The latest guidance on the actions companies should be taking for the three tier levels is available in the Inspectorate’s most recent guidance – DWI_PFAS-Guidance_Mar_2025.pdf

Monitoring by water companies has highlighted a further PFAS of potential concern; 6:2 fluorotelomer sulfonamide alkylbetaine (6:2 FTAB). This compound has been added to the parameter list and companies are expected to initiate monitoring and reporting for this parameter as soon as practicable.

Companies are also expected to consider the effect of combined concentrations of the PFAS chemicals of interest identified in the parameter list. As such, the requirement to implement a prioritised mitigation methodology to progressively reduce PFAS concentrations in drinking water has been further extended to include combined PFAS on a ‘sum of’ basis. Companies have now implemented reporting for the ‘sum of PFAS’ based on the 48 named PFAS in the parameter list. Where sites fall into tier 2 or 3 for the sum of parameter these sites should be rolled into the existing site prioritisation approach based on their relative classification and an appropriate risk reduction strategy should aim to progressively reduce PFAS concentrations in drinking water. The Inspectorate’s three tier system is a risk-based system intended to prioritise the supply systems which require additional controls. The analysis targets the source water because this provides information on the hazard and what the necessary mitigation should be, be that blending, removal of the source water or treatment. During 2024, there were no samples reported in tier 3 for any treated water being supplied to consumers. In total 351 tests of raw water abstractions had results within tier 3. This helps to demonstrate that the current industry strategy of mitigating the risks from PFAS is working effectively to protect consumers. Ninety-six percent of the tests were less than the detection limit for their analytical methodology.

Table 10 Total number of tests in England including all results less than limit of detection

Tier	Raw water tests	Treated water tests	Total
Tier 1	287,840	413,084	700,924
Tier 2	28,888	17,223	46,111
Tier 3	351	0	292
Total	317,079	430,307	747,386

Table 11 Total number of tests in Wales, not including results less than limit of detection

Tier	Raw water tests	Treated water tests	Total
Tier 1	75	443	518
Tier 2	6	0	6
Tier 3	0	0	0
Total	81	443	524

In Wales, PFBS was the most prevalent species in raw water during 2024 which was present in 23 tests (28% of total PFAS detections above the limit of detection). In Wales, the most prevalent species in treated water was also PFBS, being present in 42% of tests with detections above LoD (216 in number). The table below sets out all the other parameters which contributed greater than 1% of detections by number of samples rather than by result for all tiers in raw water. This includes the ’sum of PFAS’ parameter. For reference a total of 329,192 tests were undertaken on raw water samples in England, and 12,113 in Wales, in order to produce these results.

Where PFAS is identified, action is taken by the companies in line with the risk prioritisation strategy. In 2024, there were no detections in Wales within tier 2 and 3 in final treated water. Dŵr Cymru Welsh Water had a detection within tier 2 from Llechryd works in April 2024, however as part of the company’s investigation, it was determined that the result was a false positive due to an error within the laboratory testing process. Actions were identified to prevent a reccurrence.

Table 12 Raw water tests Wales and England (greater than limit of detection)

Wales	Tier 1 Detections	Tier 2 Detections	Total	England	Tier 1 Detections	Tier 2 Detections	Tier 3 Detections	Total
PFBS	23		23	PFOS	1499	541	74	2,114
PFBA	18	1	19	PHFHxS	1254	428	25	1,707
PFOA	10	1	11	PFOA	1603	93	7	1,703
PFHxA	3	1	4	PFHxA	1405	197	15	1,617
11Cl-PF3OUdS	3		3	PFBS	1476	49	2	1,527
PFUnDA	3		3	PFBA	1223	46		1,269
PFDoDA	2		2	PFPA	821	200	15	1,036
PFDS	2		2	PFHpA	883	10	14	907
PFHpA	1	1	2	PFecHS	216	122		338
4:2 FTSA	1		1	PFPS	264	32	3	299
6:2 FTSA; 6:2 FTS	1		1	FBSA	206	12	7	225
8:2 FTSA		1	1	6:2 FTAB	189	29	3	221
FBSA	1		1	6:2 FTSA; 6:2 FTS	97	84	13	194
FHxSA		1	1	PFDA	193	1		194
FOSA	1		1	FHxSA	134	49	10	193
MeFOSE	1		1	PFHpS	123	13		136
PFecHS	1		1	8:2 FTSA	115	9		124
PFHpS	1		1	HFPO-TA	115			115
PFNA	1		1	PFNA	115			115
PFOS	1		1	PFUnDA	111			111
PFPS	1		1	EtFOSAA	103			103
Total	75	6	81	MeFOSAA	92			92
				PFNS	92			92
				FOSA	82	9		91
				HFPO-DA (Gen X)	82			82
				PFDS	81			81
				PFDoDA	79			79
				PFHxDA	78			78
				PFODA	78			78
				PFTeA	78			78
				11Cl-PF3OUdS	77			77
				NFDHA	75			75
				EtFOSA	74			74
				PFTrDA	74			74
				4:2 FTSA	72			72
				MeFOSE	72			72
				PFEESA	72			72
				3:3 FTCA	71			71
				DONA	71			71
				PFDoS	71			71
				5:3 FTCA	2		68	70
				PFMOPrA	70			70
				PFMOBA	69			69
				PFUnDS	69			69
				7:3 FTCA	68			68
				MeFOSA	68			68
				EtFOSE	63			63
				9Cl-F3ONS	34			34
				Total	14,059	1,924	256	16,239

Table 13 Treated water tests Wales and England (greater than limit of detection)

Wales	Tier 1 Detections	Total	England	Tier 1 Detections	Tier 2 Detections	Total
PFBS	216	216	PFBA	2,939	75	3,014
PFHxA	47	47	PFHxA	1,943	361	2,304
PFOA	39	39	PFOS	1,493	214	1,707
PFBA	30	30	PFBS	1,489	14	1,503
PFOS	24	24	PFPA	1,058	384	1,442
PFUnDA	13	13	PHFHxS	1,135	167	1,302
PFDA	10	10	PFOA	1,068	57	1,125
9Cl-F3ONS	7	7	PFHpA	698		698
EtFOSAA	7	7	6:2 FTSA; 6:2 FTS	84	367	451
PFNS	6	6	6:2 FTAB	98	8	106
6:2 FTSA; 6:2 FTS	5	5	PFPS	106		106
MeFOSAA	5	5	PFDA	86		86
PFDS	5	5	FBSA	70		70
11Cl-PF3OUdS	3	3	FHxSA	40	22	62
FOSA	3	3	PFHpS	53		53
PFDoDA	3	3	PFecHS	41	8	49
PFNA	3	3	8:2 FTSA	43	1	44
PFPS	3	3	PFNA	36		36
3:3 FTCA	2	2	NFDHA	31		31
EtFOSA	2	2	FOSA	28		28
HFPO-TA	2	2	PFUnDA	27		27
PFHpA	2	2	PFNS	25		25
PFTrDA	2	2	9Cl-F3ONS	22		22
8:2 FTSA	1	1	EtFOSAA	14		14
EtFOSE	1	1	MeFOSAA	14		14
MeFOSE	1	1	PFEESA	14		14
PFUnDS	1	1	PFDoDA	11		11
Total	443	443	PFDS	8		8
			PFTeA	8		8
			11Cl-PF3OUdS	7		7
			HFPO-TA	5		5
			MeFOSE	2		2
			EtFOSA	1		1
			PFHxDA	1		1
			PFMOBA	1		1
			PFODA	1		1
			PFUnDS	1		1
			Total	12,701	1,678	14,379

Audit programme

Table 14 Audits in Wales

DWR	Customer call centre
DWR	On site alternative supplies provision
DWR	Felindre works and Pentre service reservoir
DWR	Drinking Water Safety Planning and Bryn Cowlyd site audit
HDC	Sugn y Pwll, Bronwylfa, Higher Berse, and Gronwen service reservoirs
DWR	Cwellyn works
DWR	Pen y bont works
DWR	Air Valves
HDC	Air Valves

Customer call centre

An audit of the Dŵr Cymru Welsh Water consumer call centre was conducted on 25 March 2024. The stock phrase used in response to discolouration contacts contained contradictory clauses suggesting the water was safe to drink but that the company would not expect the consumer to drink it. This could be interpreted as tacit ‘do-not-drink’ advice and the company has since revised the wording of this stock phrase to allay consumer concerns whilst investigations are undertaken. The existing data capture software used by the company can record a primary and a secondary descriptor. It cannot capture discrete multiple descriptors in compliance with Information Letter 04/2022 except through the contact narrative text. Companies are reminded of the requirement to capture data on all descriptors detailed by the consumer during a contact.

Felindre works

An audit of Dŵr Cymru Welsh Water’s Felindre works in South Wales was conducted in June 2024. Recommendations were made regarding the management of the site’s granular activated carbon adsorbers (GACs), removal of an online water quality monitor from service, GAC clean backwash tank defect resolution, a lack of triple validated monitor visibility and alarms on SCADA, password hygiene and other security arrangements. Of the site’s 12 GACs, six had exceeded the site-specific regeneration frequency of nine years. Evidence was provided to demonstrate sufficient adsorbance capacity through the provision of the most recent spent and newly regenerated media iodine numbers. Companies are encouraged to monitor suitable media exhaustion proxies at regular intervals for each adsorber in service to ensure adsorbance capacity is sufficient for all raw water loading scenarios. The site flow cap set-points were such that the minimum empty bed contact times for all water quality parameters stated in company documentation were not achievable in all operational circumstances. Site flow control philosophies should be assessed to ensure the minimum carbon contact times (GAC and PAC) defined by company procedures are accounted for. A system validation alarm for the triple validated disinfection chlorine monitors was noted on the periodically checked local human machine interface (HMI) during the site walk-around (Image 18). The alarm had been generated by an ephemeral drift from set-point of one of the chlorine monitors and was not evident on the site SCADA system. Companies should ensure that all alarms relating to disinfection control are captured by associated apprehension systems to ensure site operators address any defects as soon as is practicable. The storage of sodium hypochlorite used in a temporary dosing arrangement was found in a room without temperature controls and final water chlorate sampling had not been organised (Image 19). Companies are reminded of the requirement for all sodium hypochlorite to be stored in accordance with the requirements of BS EN 901:2013 and to monitor associated byproducts in dosed water. A handwritten note with a historic site SEMD password was found in the site control room. Companies are reminded of the importance of password hygiene to ensure such security measures are effective.

Image 18 Chlorine HMI

Image 19 Temporary hypochlorite arrangement

Cwellyn works

An audit at Dŵr Cymru Welsh Water’s Cwellyn works was conducted in August 2024, as part of the Inspectorate’s risk-based audit programme. The works gained national attention in 2005 when it became the centre of a Cryptosporidium outbreak, resulting in 231 confirmed cases of cryptosporidiosis and subsequent legal action against the company. In response, the treatment works underwent substantial upgrades, including the installation of ultraviolet treatment for Cryptosporidium inactivation.

The 2024 audit focused on the work’s disinfection processes and policy. Following the review, seven recommendations were made to the company, addressing chemical dosing, security measures, and improvements to its disinfection policies.

A key concern raised during the audit was an unprotected sample line entering the contact tank through a hatch, posing a potential security risk. While the company has acknowledged the issue and documented it in its risk register, no action had been taken to mitigate the risk until it was flagged by inspectors during the audit.

Image 20 Unprotected sample line on contact tank roof

A full resolution could not be implemented while the contact tank remained in supply, necessitating significant engineering works to enable corrective measures. Following the audit, a temporary repair was introduced to enhance security arrangements while plans for the tank’s removal were developed. The company was recommended to review its procedures, escalation processes, and governance framework to ensure that similar issues and potential resolutions are identified more effectively in the future. Additionally, a recommendation was made to reassess the risk evaluation methodology to better integrate security risks into the overall assessment process, ensuring they are appropriately documented and addressed where relevant.

Image 21 New temporary repair to provide protection for sample line

Although Cwellyn works has not yet experienced taste and odour issues in distribution, the company has encountered such concerns at other surface water sites in recent years. There is currently no specific treatment process at this site, for removing taste and odour compounds such as 2-methylisoborneol (MIB) or geosmin, though biological activity in the filters may provide some mitigation. A recommendation was made for the company to review its short, medium, and long-term strategies to minimise this risk and establish contingency plans. These plans should ensure a proactive response to prevent an escalation of related risks, including taste, odour, and the presence of MIB and Geosmin.

With climate change increasing the likelihood of extreme heat events and drought, companies must regularly reassess their risk assessments and plan their response measures to remain resilient in the face of evolving environmental challenges.

Penybont works

Four events occurred at Dŵr Cymru Welsh Water’s Penybont works involving elevated turbidity within the disinfection process across 2023 and 2024. Each event involved the management of turbidity risks within a rising main from the site to an offsite distribution cum contact tank. A reactive audit of the site was conducted in September 2024 in response. Several risk factors were identified during the visit with recommendations made. The company has since installed a turbidity monitor at the inlet to the tank and a downstream diversion to waste facility to enable containment and disposal of water where required. A weekly conditioning programme for the main has also been initiated to mitigate the further build-up of sediment. Enforcement action has also been taken in the form of company-wide notices to deliver improvements in disinfection process management processes.

Air valves

All Welsh companies were subject to an industry-wide audit of their air valve management practices.

Both Hafren Dyfrdwy and Dŵr Cymru Welsh Water use the Water Industry Mechanical and Electrical Specifications (WIMES) 8.09 document to inform asset standards for company air valves. This industry standard provides the opportunity for deviation from manufacturer recommendations regarding original design function and ongoing performance management. Where equipment is installed within supply systems it is critical that manufacturer guidance is followed to ensure ongoing satisfactory performance. Failure to do so represents a risk to both operability and water quality.

The records kept to demonstrate compliance with industry standards for air valves were in many cases unavailable. In addition, records of reactive remedial works following identification of defects during air valve inspections were unavailable. Companies are reminded that good record keeping is essential in the demonstration of effective risk management. The companies have and are reassessing the risks to water quality posed by air valve management and the relative risks associated with different applications and locations. To this end, new inspection and maintenance regimes based on this assessment have been and are being formulated. The Inspectorate welcomes this approach and encourages the companies to reflect on these assessments, inspection methods and regimes to improve the management of these risks.

Service reservoirs

The wider industry and Wales were both audited to understand the health of network water storage assets. A Dŵr Cymru Welsh Water service reservoir was audited in June 2024 as part of the water treatment works audit. Four Hafren Dyfrdwy service reservoirs were audited in August 2024, attracting seven recommendations regarding documentation of company site audits (two), sodium hypochlorite storage conditions, sampling arrangements at ebb/flow service reservoirs, air valve inspection records, sampling facilities, and the risk assessment categorisation of a membrane in use in excess of its asset life. In addition, ten suggestions were made across these four sites.

Recommendations

If a regulatory breach occurs or seems likely, and an Inspector cannot determine that the occurrence will not happen again, they must issue a formal recommendation to the company. These recommendations serve to highlight areas where companies can improve compliance with the Regulations. Each recommendation is tracked to assess its significance and the company’s response. This regulatory strategy aims to pinpoint companies at risk of regulatory failure that could increase residual risk to the drinking water supply, ensuring necessary improvements are made.

Inspectors made 123 recommendations in 2024. See Figure 34. Dŵr Cymru Welsh Water entered into transformation in June 2024. In the months leading up to this, the Inspectorate conducted a comprehensive review of the company’s data, information, and performance over the previous three years to support its decision. By the time the company’s position was confirmed, the Inspectorate had already devised plans to enhance its regulatory activities, which would accelerate the establishment of the transformation programme. A key focus of these efforts was technical auditing, resulting in a higher number of site technical audits in 2024 compared to previous years. This increased scrutiny enabled the Inspectorate to determine additional areas for improvement that had not been previously identified. The additional technical audits resulted in a step-change increase in audit recommendations in 2024. A notable sub-set of the audit recommendations that can be seen in Figure 34 were those made in response to the DWSP audit which was comprehensive and a ‘deep dive’ of the company’s complete DWSP system. The Inspectorate anticipated an increase in audit recommendations during the first year of transformation. These recommendations should be seen as part of the establishment of transformation rather than a deterioration in performance. Hafren Dyfrdwy received 10 audit recommendations in 2024 compared with six in 2023 and three in 2022.

Figure 33 Number of recommendations per company in 2024

Company	Number of recommendations
Dŵr Cymru Welsh Water	95
Hafren Dyfrdwy	26
Albion Eco	2

Figure 34 Trend of recommendations in Wales

Compliance	Event	Legal Instrument
2	7	0
28	22	1
15	30	0
30	37	1
13	37	0

As part of Dŵr Cymru Welsh Water’s transformation programme, thematic meetings have been introduced to concentrate on key areas, ensuring measurable outcomes. One such theme is recommendations, which hold particular significance due to the recommendations risk index—one of the factors considered when assessing whether a company should enter transformation. The main aim of this thematic meeting is to support the company in improving its RRI after three years of deteriorating performance. At these meetings, Inspectors discuss examples of responses to recommendations that are examples of the different response assessment scores available to them as part of the assessment procedure. Some of the early lessons learned from these focussed discussions included:

How to monitor the fulfilment of recommendations to the point of delivery with evidence.
What does delivery evidence look like? What is good quality evidence verses poor quality evidence?
How to determine the correct people to ‘own’ different types of recommendation.

The meetings are also an opportunity to discuss the fulfilment of current recommendations to help guide the company towards receiving a more favourable response assessment.

Figure 35 shows that management deficiencies account for the largest share of recommendations, with 77 making up this portion. Sampling, storage and distribution and treatment deficiencies also attracted recommendations. Of the 77 recommendations in the management category, the majority were for risk assessment and policies and procedures.

Figure 35 Management recommendations by type

High category			Sub category
Management	77	Wales	Risk Assessment	38	Wales
Sampling	14	Wales	Policy/Procedure	15	Wales
Treatment	13	Wales	Treatment	8	Wales
Communication	9	Wales	Investigations	7	Wales
Storage and Distribution	7	Wales	Reservoir / Network operation	5	Wales
Other	2	Wales	Disinfection	5	Wales
Catchment	1	Wales	Training	3	Wales
			Record keeping	3	Wales
			Unwholesome water	2	Wales
			Regulation 31	2	Wales
			Monitoring equipment	1	Wales
			Storage of spares / chemicals	1	Wales

Both Dŵr Cymru Welsh Water and Hafren Dyfrdwy attracted recommendations for reportable events, with 37 recommendations given in total in 2024, the same number as in 2023, between 18 events (12 in 2023). Dŵr Cymru Welsh Water received 24 recommendations between 13 events and Hafren Dyfrdwy received 13 recommendations between five events.

The recommendations risk index (Figure 36) measures all companies’ performance in recommendations against the industry. Recommendations are the first level of regulatory intervention, in line with the Better Regulation framework. For the purposes of discussion, an equal distribution of recommendations by company size (population serviced) is assumed. Regression analysis can be seen in Figure 36 as the central black line. A position below this line means a company is receiving fewer recommendations and/or lower scores attached to those recommendations than would be expected. A position above the black line means the opposite. Any measure has a degree of uncertainty and so a 95% confidence interval is applied either side of the black line, represented by the red and blue lines.

Figure 36 Recommendations Risk Index

	Expected	Final
Dŵr Cymru Welsh Water	627.2058663	1289.544909
Hafren Dyfrdwy	43.01312443	220.0270191
Albion Eco	0.036565422	0

The recommendations risk index shows Dŵr Cymru Welsh Water and Hafren Dyfrdwy’s position compared to the expected recommendation score for the company size. Whilst Hafren Dyfrdwy is within the expected scoring, Dŵr Cymru Welsh Water remain above the red line, which is expected as the company is on the start of its transformation journey.

Enforcement

The Inspectorate publishes the drinking water quality legal instruments on its website under company improvement programmes. Security (SEMD and NIS) legal instruments are considered sensitive and therefore are not published in the public domain. A summary of the legal instruments issued in 2024 is below.

Type of legal instrument	Number	Companies
Regulation 28(4) notice relating to risks identified in water safety plans	10	Dŵr Cymru Welsh Water (7), Hafren Dyfrdwy (3)

The individual legal instruments listed above have been discussed in detail, within the quarterly Chief Inspector’s reports published throughout 2024.

2024 saw the majority of work to secure legal instruments for the delivery of improvement programmes committed to by companies during PR24, reflected in the additional legal instruments summarised in the table below. These legal instruments enable the Inspectorate to monitor the progress of company plans to address drinking water quality, NIS or SEMD risks. In its PR24 determination, Ofwat have linked the price control deliverables for enhancement schemes to the Inspectorate’s issued legal instruments. The Inspectorate shall continue to work closely with Ofwat and keep them updated throughout the AMP.

Type of legal instrument	Number	Companies
Regulation 28(4) notice relating to risks identified in water safety plans	4	Dŵr Cymru Welsh Water (4)
Undertaking accepted under section 19(1) of the Water Industry Act 1991 for drinking water quality improvements	3	Dŵr Cymru Welsh Water (2), Hafren Dyfrdwy
Undertaking accepted under section 19(1) of the Water Industry Act 1991 for SEMD improvements	5	Dŵr Cymru Welsh Water
Regulation 17(1) notice for improvements under the Network and Information Systems Regulations 2018	2	Dŵr Cymru Welsh Water, Hafren Dyfrdwy
Formal acknowledgement of a set of actions (‘Acknowledged Actions’)	1	Dŵr Cymru Welsh Water

Transformation Programmes

A key activity of the Inspectorate’s Enforcement Team is the management of the transformation programmes. The Inspectorate may initiate a transformation programme where the risk position of a company becomes elevated or is frequently realised in a specific area of operation. For example, multiple, similar drinking water quality events caused by a lack of appropriate training. Once a company is notified that the Inspectorate intend to place them into transformation, they seek to work collaboratively to put together a measurable programme of improvements.
A transformation programme includes a set of bespoke legal instruments to address those areas of high risk. They are generally large in scope and require a long-term, concentrated effort to move the risk position. Following the initial tranche of legal instruments, follow up legal instruments may be served to address issues that fall out of the initial programme.

Transformation is not only about completing the work included in legally binding notices, but it is about a robust and consistent effort to reduce overall risk. A large factor in this can be the attitude of company personnel, particularly those in senior leadership roles, who ultimately determine the attitude of the company.
Dŵr Cymru entered transformation in June 2024 following an increasing risk profile as demonstrated by the company’s event and compliance reports and the subsequent assessment by the Inspectorate and the high number of recommendations these reports generated.

The transformation programme has been developed in collaboration with the company during 2024 and aims to improve performance in a number of key areas such as training, governance, procedures, and a hazard review of risks at water treatment works. Five transformation notices were served on the company at the end of 2024.
As part of routine work alongside the transformation programme, a new discolouration target for AMP8 was agreed with the company, however there remains to be any significant improvements in the company’s performance against this metric, to bring it to industry average. The new AMP8 target is a stretching target of a 50% reduction on the AMP7 target, with the aim that by the end of AMP9, the company will align with the rest of the industry.

The company has requested discussion and constructive feedback on milestone reports, recommendations and other aspects to deliver improvements which is positive and the company has stated an aim to be more open and collaborative as a whole, which of course is welcomed. The Inspectorate has started to see improvements in the submitted reports following these discussions, and encourage the company to continue in this fashion.
The Service Reservoir and Tank Inspection notice has been well managed, even with known access complications to some of the assets, the company addressed this within its planning and the company completed this notice on time, by March 2025.

The approach the company took to the transformation notices, in particular the Hazard Review notice was well-thought out, and the company appear to be placing the right level of personnel and support in the management of the notices to ensure its success.

The company is keen to have discussions and feedback regarding recommendations, milestone reports and other assessments by the Inspectorate. However, there remains some defensive or sensitive reactions during these meetings. Whilst a defensive posture is very natural, the Inspectorate’s goal is to aid the company in their understanding of our expectations and to move the company into a position where its risk profile decreases.
The company has shown eagerness to complete the transformation programme as expeditiously as possible. However, it must remember that some culture shifts take longer to embed, and whilst the Inspectorate commend the enthusiasm, the company must accept that these programmes take several years.

SEMD

2024 was the third reporting year for companies since the Inspectorate has regulated the Security and Emergency Measures Direction 2022 (the Direction). Companies have demonstrated an overall improvement in recognising the areas that they need to improve and move towards compliance with the Direction, resulting in significant investment in PR24 over a range of schemes consisting of security and emergency planning improvements.

During 2024, the Inspectorate observed increased engagement from the industry looking to proactively enhance compliance with the Direction, for example the Inspectorate hosted an emergency planning specialist from a water company who was seconded to the Inspectorate for a six-month period, under our better regulation programme. This enabled the company to gain firsthand knowledge and regulatory understanding of the Inspectorate’s expectations of water companies’ compliance with the Direction as well as the Inspectorate gaining an insight into the practicalities experienced by water companies when planning and running emergency incidents. The Inspectorate undertook a program of audits as well as event assessments and company interaction which resulted in a range of enforcement activity to secure improvement and compliance as demonstrated in Figure 37.

Figure 37 : SEMD enforcement overview

Enforcement orders made	2
Undertakings served	4
Recommendations made	86

The industry has fed back that this enforcement led approach is a notable change from the previous regulatory approach, prior to the Inspectorate’s involvement.

Water companies have made notable progress in complying with Direction requirements, with evidence of improved outcomes and compliance emerging, with more to deliver in AMP8.

RAG (Red/Amber/Green) submission

2024 was the third year for the risk assessment RAG returns, as companies continued to work to benchmark against the expectations of the Direction and the rest of the industry.

Overview of RAG movements

Since 2022, the companies’ red and amber self-classifications have increased, as expected in the initial years of assessment following feedback of events and audits and peer to peer benchmarking:

Figure 38 RAG changes by year

	2022	2023	2024
Green	433	454	392
Amber	80	84	96
Red	18	9	30

The most significant shifts in RAG status typically follow an audit or major event.
In contrast to previous years, the greatest movement in 2024 was observed in the Testing and Exercising category, coinciding with industry-wide audits being submitted alongside RAG assessments.
Inset appointees are not represented in the datasets, as they follow a different reporting mechanism.

Notable RAG outcomes include:

Vulnerable consumers

Like last year, many companies reported amber and red for vulnerable customers. Several companies cited problems with linking existing Priority Service Register (PSR) customer data with customer systems as well as highlighting issues of data sharing agreements and varying support from external agencies, such as Local Resilience Forum (LRF) partners, providing uncertainty about the ability to meet the demand for vulnerable consumer deliveries.

Several companies have developed systems to improve liaison with vulnerable consumers. South East Water introduced a new SMS text messaging system of informing vulnerable consumers of water disruptions. Companies reporting green had detailed information on vulnerable sites in their remit, for example using tactical mapping processes to identify vulnerable customers such as hospitals, schools, nursing/care homes and prisons. Several companies had hospital and prison plans in place containing key information to increase understanding and support of these customers during any incidents.

Testing and exercising

The 2024 RAG submission coincided with an industry wide audit of testing and exercising, and the 2024 submission saw numerous companies move to amber in their RAG status for these outcomes. Several companies reporting amber had not exercised their reasonable worst-case scenario in terms of alternative water provision. We saw one company recognising this and they are now looking to exercise their biggest island zone. Other companies noted a lack of testing of vulnerable sites such as prisons and hospitals.

Some companies listed several ‘live incidents’ as testing and exercising but did not identify which objectives were met and which were still outstanding, with limited post incident reviews to maximise the learning. Some companies have implemented a post incident review process to capture learning after each incident and exercise, which is supported by centralised action trackers to monitor progress of actions and a governance framework in place to escalate overdue actions; this was welcomed by the Inspectorate. Most companies carried out testing and exercising with LRF partners, however other companies only took part in LRF organised exercises and took limited learning from these, whilst others proactively organised and engaged with the LRF in water related incident scenarios, this was also welcomed by the Inspectorate.

Those companies reporting green for the testing and exercising outcome typically undertook live emergency planning testing with external stakeholders as well as several companies testing a variety of alternative water deployment, from setting up alternative water stations, deployment of static tanks and tankering exercises. These exercises had clear aims and objectives with documented learning embedded in the company. In addition, several companies reporting green had undertaken a variety of security testing including penetration testing of sites and assets, bug sweeps, email phishing tests, as well as the placement of dummy signs at a site to test security reporting exercises.

Identification of external suppliers

Companies reporting green used tools such as risk ledger where businesses with heightened security risks are signed up to the platform providing an assessment of the security risks posed by these organisations. In addition, other companies mandated that their supply chain are required to complete criminal declarations, and identification checks before work on operational assets with access to sites being a controlled process requiring sign off. One company implemented personnel security checks for temporary employees delivered to the same standard as those conducted on employees.

Events and incidents

Social media auditors have presented a challenge for several companies during 2024, and whilst they are normally legal, this has highlighted several issues for the companies involved. There were, however, a few examples of positive behaviours around challenging and engaging with the social media auditors.

Over the year the Inspectorate engaged with several companies regarding revealing too much information about sensitive sites, this can be from site tours which are specifically prohibited, to industry write-ups on large construction projects. The Inspectorate reminded and continues to remind companies of their obligations to keep critical information secure.

Notable events include:

Southern Water – Hastings loss of supply

Between 2 May 2024 and 7 May 2024, consumers supplied from a treatment works in Hastings lost drinking water supplies due to a burst on the incoming raw water main supplying the works. This was notified to the Inspectorate as drinking water quality event 2024/9637. During the event, the company failed to comply with the requirements of paragraphs 3 and 4(4) of the Direction.

The company has previously acknowledged that the main required replacing, but this was not done due to cost. It was noted on the company water safety plan as a ‘DWI category D’ requiring further mitigation as well as being the cause of a previous loss of supply and burst event. Therefore, the Inspectorate concluded that the company did not have in place adequate resilience plans to ensure the continuance of all its water supply functions, which is a breach of paragraph 4(4)(a) of the Direction, that states that plans for water supply must be prepared on the basis that the company must (a) continue to carry out (i) all of its water supply functions.

Therefore, following the event, the Inspectorate enforced, and the company has offered as section 19 undertaking to replace the main and improve resilience to the area.

Affinity Water YouTube incident

The event concerned YouTube content creators gaining unauthorised entry and filming water company tunnels at a reservoir and borehole site, bypassing security measures and entering through an insufficiently secured door. The resulting video, uploaded in January 2024, prompted the company to investigate and report the incident to the Inspectorate. The security breach was attributed to a faulty lock, and the company acknowledged delays in alarm response. Remedial actions included securing the door with additional locks, installing a secondary security detector, and implementing regular maintenance checks as a short-term measure. The door was subsequently replaced with measures put in place to address the alarm response.

The Inspectorate recommended a comprehensive review of the company’s security maintenance strategy and communication protocols. The Inspectorate emphasised the need for timely alarm responses and thorough checks of all access points. The company was required to submit a detailed review of site security, confirm the security rating of new door fittings, and ensure that future breaches are detected and addressed promptly.

Thames Water Guildford loss of supply

Following an extreme weather incident at the end of 2023 (storm Ciaran), the company experienced power outages at eight pumping and treatment sites across the Guildford supply system and a subsequent widespread loss of supply was experienced across the Guildford area. This was due to the number and duration of power outages at Shalford treatment works during this period, as well as the lack of water/power supply resilience within the Guildford system.

Following the Inspectorate’s assessment of the event, the company was sent a ‘minded to enforce letter’ requesting a section 19 undertaking to be signed by the company to deliver improvements to emergency planning and power resilience within the Guildford area. The company accepted the section 19 undertaking in November 2024 which requires the company to carry out action to improve resilience in the Guildford area.

Southern Water Testwood loss of supply

A significant water quality event at Testwood works occurred on December 18, 2024, involving plant failure and loss of supply. The event led to elevated turbidity levels and subsequent shutdowns, causing a loss of supply for 130,920 consumers. The company took various actions, including forming an incident team, setting up bottled water stations, and rezoning their network to bring in water from other areas. The company stated they faced challenges in setting up bottled water stations and ensuring timely deliveries, impacting their ability to provide the required minimum water supply to affected consumers.

The Inspectorate in its investigation, highlighted the need for better planning and execution of alternative water provisions during emergencies and recommending reviewing the company’s methodology for assessing bottled water station locations and improving the resilience of alternative water supplies, particularly for vulnerable sites like hospitals. Additionally, the need to review network storage and response capabilities to handle similar incidents more effectively in the future was highlighted. A ‘minded to enforce’ letter, requesting a section 19 undertaking was sent as part of the event write up, requiring the company to undertake works to increase resilience at the site.

Southern Water secure minded communications

In January 2024 the Inspectorate wrote to Southern Water regarding an online article that showed detailed valve drawings of a Critical National Infrastructure (CNI) site. There were several concerns with this article including that it revealed locations of sensitive assets and listed names of the key supply chain used to deliver this project.

The Inspectorate formally recommended the company ensure that future publications do not reveal sensitive information within the article, and suggested that the company removed this existing article from the website. The company responded by removing the article, stating no further articles relating to CNI sites will be published and relevant processes and procedures reviewed around publication of information.

Table 17 – Audits undertaken by the SEMD team in 2024

Company	Audit area
TMS	Physical	CNI Security	Jan-24
TMS	Physical	CNI Security	Jan-24
TMS	Physical	CNI Security	Jan-24
AFW	Physical	CNI Security	Jan-24
SRN	Physical	CNI Security	Feb-24
AFW	Desktop	Testing and Exercising	Apr-24
ANH	Desktop	Testing and Exercising	Apr-24
DWR	Desktop	Testing and Exercising	Apr-24
HDC	Desktop	Testing and Exercising	Apr-24
NES	Desktop	Testing and Exercising	Apr-24
PRT	Desktop	Testing and Exercising	Apr-24
SES	Desktop	Testing and Exercising	Apr-24
SEW	Desktop	Testing and Exercising	Apr-24
SRN	Desktop	Testing and Exercising	Apr-24
SST	Desktop	Testing and Exercising	Apr-24
SVT	Desktop	Testing and Exercising	Apr-24
SWB	Desktop	Testing and Exercising	Apr-24
TMS	Desktop	Testing and Exercising	Apr-24
UUT	Desktop	Testing and Exercising	Apr-24
WSX	Desktop	Testing and Exercising	Apr-24
YKS	Desktop	Testing and Exercising	Apr-24
BRL	Physical	CNI	May-24
SES	Physical	Command and Control	Jul-24
HDC	Physical	CNI Security	Oct-24
YKS	Physical	CNI Security	Nov-24

NIS

The Network and Information Systems Regulations (2018) is a regulation to ensure the operational technology which maintains the production of drinking water remains robust and operational, to ensure water is delivered at all times. In England and Wales, the implementation and operational delivery of the NIS Regulations is delegated to the Drinking Water Inspectorate. The strategic purpose is to ensure that water companies deliver the essential service of providing uninterrupted, wholesome water supplies to consumers in England and Wales.

Water companies serving a population of 200,000 people or more must implement a risk assessment to improve resilience of operational technology, returning the outcome as part of the regulations annually since 2018.

Between 2023-2024 every water company has been subject to an Inspectorate cyber resilience audit to verify each company’s self-assessed risk assessment. Two companies were issued with legal notices to improve their risk assessments in response to the audits. Every company in England (and Wales) has a regulation 18 notice to address residual cyber risk and their PR24 cyber improvement plans. Ofwat Price Control Deliverables are tied to these notices being met in full. Failure to meet the notice requirements may attract Ofwat penalties in addition to any Inspectorate enforcement. Due to the sensitive nature of cyber resilience in the Water sector, information on sector performance is not published on the public domain. A Ministerial report on Cyber Resilience in the water sector is produced annually.

Materials in contact with drinking water (Regulation 31)

Regulation 31 prohibits a water company from applying any substance or product to, or introduce any substance or product into water, which has not met one of the provisions in regulation 31 of the Regulations. This covers all chemicals and construction products used by water undertakers, from the source of the water, up to the point of delivery to the consumer’s premises. This is a critical duty because materials can contaminate water by taste, odour or by leaching of harmful by-products. The regulation sets out how approvals can be given to construction products and materials that do not prejudice water quality and ultimately consumer safety. During 2024, the Inspectorate continued to receive and process applications for approval of products in contact with drinking water (under regulation 31). The volume of applications processed was:

Table 18 Regulation 31 applications

Year	Total applications	New applications	Product changes	Product reapprovals
2024	177	47	79	51
2023	126	24	61	42
2022	145	32	62	51
2021	146	23	62	60

The Inspectorate has continued working with its IT partners to further develop the regulation 31 portal for product approvals. The system has replaced the previously used manual application forms with online, interactive application forms that will guide applicants in providing all the necessary information for an approval or product change to be considered. The online process will have the benefit of meeting accessibility standards, making them available to more people with the next phase of the project delivering and end to end process and approved products list transformed from a monthly, published PDF document to an interactive, searchable website which is updated in real-time. This will effectively become a live, online catalogue of approved products.

2024 saw a significant increase in poor product stewardship with several approved products revoked from the Secretary of State’s List with immediate effect and a prohibition issued for the use of a product with an unauthorised name change. Subsequent investigations led to further revocations in early 2025. All identified issues were as a result of unauthorised changes being made to the product.

In December 2024, approval for Puriton Pipes (DWI 56/4/1112) manufactured by Radius Systems Ltd was revoked. The company had made a late submission for reapproval and once all the relevant documents were submitted, reapproval was granted. Subsequently however, the Inspectorate was informed that the information provided was incorrect and that unauthorised changes had been made to the product. This resulted in immediate revocation of the approval and extensive liaison with the company.

A notification letter of prohibition was issued to the industry following an unauthorised name change to an approved product. As part of a rebranding process, MBCC provided suppliers with products re-labelled with a handwritten label stating the product’s new name, changing from Sikadur-CombiFlex 930 to Sikadur-CombiFlex 933 (DWI 56/4/1569), accompanied by the MBCC IFU document for MasterSeal 930 joint bandage with MasterSeal 933 adhesive (DWI 56/4/144), the product and IFU names not aligning. This was initially identified by Northumbrian Water who notified the Inspectorate and was subsequently found to be a widespread issue. The company had not completed the change process for this product which resulted in several companies having to remove the product from assets where it had been applied, with other companies forced to keep assets out of supply until the process had been completed and the name change authorised. This resulted in a significant number of meetings with company representatives to rectify the issue.

This was yet another example of both poor product stewardship by the manufacturers and complacency on behalf of water companies and contractors who failed to identify that the IFU did not match the label on the product container and the product name did not appear on the Secretary of State’s List. As a result, water companies were instructed to notify use of this product to the Inspectorate as a water quality event.

The Inspectorate does not take the decision to revoke products or prohibit the use of products lightly, however, where the requirements to maintain product approvals are not met, and constitutes a potential risk to public health

In addition, several approval holders omitted to apply for product reapprovals which resulted in an increase in expired products, and manufacturers having to undertake the process of product approval, rather than re-approval.

These incidents were extremely time consuming for the Inspectorate to resource and impacted the growing back log of applications. A list of all products approved and under consideration under regulation 31 is available on the Inspectorate’s website: https://www.dwi.gov.uk/drinking-water-products/resources-for-water-companies/approved-considered-products/

Anglian Water – Regulation 31 Case

At Northampton Magistrates Court on 15 May 2025, Anglian Water were fined a record £1.42 million following a prosecution by the Inspectorate for drinking water failures affecting around 1.3 million people.

Between June and December 2021, Anglian Water notified the Inspectorate of four water quality events due to the use of unapproved pipework and material used in several tanks in the supply of drinking water. Anglian Water Services Limited pleaded guilty to five offences under regulation 33 of the Water Supply (Water Quality) Regulations 2016 (as amended) for repeatedly introducing unapproved materials into the water supply. The investigation identified compelling and credible evidence for the following failures and findings on four separate sites and schemes.

Issues common to each event

The investigation identified compelling and credible evidence for the failures and findings below (common to all four schemes):

Lack of control of the regulation 31 process to prevent the installation of unapproved products in a submerged environment repeatedly (strong evidence pointing to failure to control products used, backed with witness statements, contractor witness statements, photographs and Materials in Contact records).

Poor management of contractors and supply chain/procurement arrangements (backed by witness statements, procurement and delivery records).

Lack of regulation 31 training in place at the time of installation for engineers, water quality, or project managers (training records, witness statements).

The coating of the pipes (in all events) deteriorated to a powder/flakes that was easily removed from the surface of the pipes. The analysis of the coatings contained controlled phthalate-based substances, some of which are banned from children’s toys, cause birth defects and cancers (evidence includes compound analysis reports, SNARLS, pictures, and witness statements).
General compliance samples have not detected a deterioration in quality (except at Kedington, see below) – but not all relevant parameters were analysed regularly and consistently (evidence includes sampling records).

Picture 1866970860, Picture

Approximately 1.3 million customers across the Anglian Water region have been impacted by these failures. The Inspectorate was critical of the wrong products being used in submerged environments, lack of controls and of the company’s management of products. The Inspectorate was also critical that an asset remained in service after it had been identified that non-approved products were being used.

Hannington Reservoir 1A and 1B – Tank A in supply from April 2016 to December 2021. Tank B in supply to present day.

Pitsford Storage Tank B – in supply from October 2016 to December 2021

Diddington Reservoir – in supply from Feb 2017 to November 2021

Kedington contact tank and balance tanks – in supply from March 2020 to May 2020

Failure to control the installation of unknown and untested materials can have consequences; this prosecution serves as a reminder that drinking water must come first as a service.

Research publications

The following research projects have been published throughout 2024.

Dual pipe water recycling systems and risks to water quality

Published 20 February 2024 Ref: DWI 70/2/346

This report comprises of the outputs of a study conducted on behalf of Defra and the Drinking Water Inspectorate to gather current knowledge on dual pipe water recycling systems at both national and international levels. The aim of this research is to review the current risks from such systems and the suitability of English and Welsh regulation to manage these risks and evolving systems.

The research project found that many large scale dual pipe systems in the UK have either been mothballed or have never become operational. The reasons for this are unclear, but international experience suggests cost, maintenance, and inconsistent public support for recycling are factors.

The research suggests some actions for further evaluation, to reduce the risks and enable the safe expansion of dual pipe systems and water recycling schemes, including:-

Separate regulations for dual supplies and drinking water regulations, to provide a coherent governance framework for recycling schemes.
Comprehensive types of dual pipe schemes (in terms of both source water and end uses).
Targets for water quality based on the source water and the intended use.
A single source of updated guidance for scheme designers, installers, and operators.

The research project has highlighted opportunities to resolve guidance differences between regulators and legislators. Water quality legislation does not currently distinguish between water for bathing or consumption and water for other domestic purposes (such as toilet flushing). Currently, all water used for domestic purposes must be wholesome (i.e. of a drinking water standard) as per the relevant water quality legislation.

Impact and future of the regulatory model and legislative framework surrounding private water supplies in England and Wales

Published 15 May 2024 Ref: DWI 70/2/352

The Inspectorate commissioned research on the regulatory framework and regulation of private water supplies (private supplies) to understand its impact and how this framework could be improved to safeguard consumers of private water supplies. This research was undertaken by WRc, and they have produced separate reports for England and Wales.

Although public and private supplies are subject to the same water quality standards, the risk assessment and monitoring of these supplies and resulting enforcement is less rigorous. Current drinking water quality legislation does not safeguard the health of all consumers equitably. A significant legislative gap means that single dwellings with a private water supply, which constitute a significant proportion of the total, are not subject to regular risk assessment and monitoring. The number of water quality tests which fail the standard for total coliforms and E. coli is around one hundred times greater from private supplies than from the public water supply.

While there has been an improvement in compliance with standards since 2010, most likely due to regulatory activities being focused on prioritised regulation 9 supplies (large, plus any used for commercial or public activity) progress from 2020 onwards has stalled. Due to the variability, inconsistency, and inadequate mechanism for collecting and collating private water supplies drinking water quality data, it is not possible to demonstrate an evidential link between the introduction of risk assessment activities and its impact on water quality.

There are economic barriers to connecting private supplies to public water supplies, where it is feasible, resulting in public supply connections being a non-viable option, even when a private supply poses a risk to health.

Local authorities are the regulators of private supplies, but the availability and funding of sufficient experienced practitioners in local authorities results in the Regulations not always being enforced, drinking water quality sampling sometimes being inadequate and mandatory risk assessments not always being in place. None of the local authorities interviewed as part of the research, commented that they routinely enforce based upon risk assessment alone, in the absence of failed test results.

Progress is recommended in areas including legislative harmonisation, a review of risk assessment and sampling practices, and the provision of additional powers to regulate and audit. The evidence from the review and stakeholder engagement suggests that a revised regulatory framework would deliver significant benefits in the medium term, without the need for centralised regulation. To resolve the uneven application of the legislation by local authorities, training and toolkits should be provided, and the sharing of good practice and collaboration should be facilitated. The report made a number of recommendations for areas including the creation of an overseeing body with the powers to enforce and audit. The relevant legislation should be harmonised and modernised, additional resources should be found for local authority private water supply teams and additional independent research should be commissioned.

Cyanotoxins in raw surface waters

Published 13 August 2024 Ref: DWI 70/2/343

This project aimed to determine the scientific relevance of any prescribed standard for Microcystin-LR (MC-LR), its occurrence in raw surface waters, treated water concentrations, risks to consumers, and the suitability of analysis methods for cyanotoxin monitoring.

Cyanobacteria produce a wide range of cyanotoxins that are potentially hazardous to health. A health Guideline Value (GV) of 1.0 µg/L of total (intra + extra cellular) microcystin-LR in drinking water has been proposed by the World Health Organisation (WHO) and has been adopted by the Scottish government. However, this compound only needs monitoring “in the event of a potential bloom”.

The need to understand the occurrence of cyanotoxins and their potential risk is exacerbated by the increasing frequency of bloom occurrence as a result of climate change and accelerated rates of eutrophication due to human activities such as farming and (treated) wastewater effluent. Consequently, there are a wide range of policies that could have an impact on cyanotoxin occurrence.

A survey of water companies found that whilst cyanobacteria were commonly detected in UK drinking water sources, microcystins (the only cyanotoxin monitored) were infrequently detected and at low concentrations. A review of current literature also demonstrated that there is no universal definition for an algal bloom, which undermines any proposed requirement that microcystin-LR (MC-LR) only needs monitoring in the event of a potential algal bloom.

A single analytical method was developed for the detection of MC-LR, MC-RR, MC-YR, MC-LA, cylindrospermopsin, anatoxin-a (nodularin) by reverse phased LC-MS (liquid chromatography-mass spectrometry). A separate method using HILIC (hydrophilic interaction liquid chromatography) LC-MS was developed for the detection of saxitoxin.

Cyanotoxins were monitored throughout 2023 in raw and final waters at five sites in England and Scotland. Microcystins were detected in raw water at two out of the five sites and concentrations were mostly <1.0 µg/L (< 0.2 µg/L outside of the summer months and generally < 0.5 µg/L during the ‘peak’ season).

No cyanotoxins were detected in the final waters indicating that the risk to consumers is low.

It is recognised that the data generated in this study is only representative of one year. Risk from cyanotoxins should remain under review given that the frequency of algal blooms are expected to increase with climate change.

Prevalence of viruses and somatic coliphage in UK waters – method development and data gathering

Published 13 August 2024 Ref: DWI 70/2/339

The main aim of this work was to enhance risk-based preventative strategies for maintaining drinking water safety by providing precise data on the prevalence and elimination of enteric pathogenic viruses at drinking water treatment plants in the UK. Given the current data deficiency regarding virus prevalence in UK drinking water sources, this research offers a novel perspective through appraisal of UK drinking water sources providing baseline measurement of somatic coliphage levels.

This research accomplished two key objectives:

optimised procedures for viral concentration and extraction from both surface and groundwater sources.
quantified the presence of somatic coliphages across 13 different drinking water sources, documenting their removal at different treatment stages based on 96 sample analyses.

Notably, no somatic coliphages were detected in the final treated drinking water samples, validating the efficacy of most current drinking water treatment works procedures in adhering to the European Union’s requirement of nil plaque forming units (PFU)/100 mL. The study provides insights into drinking water sources with the identification of sources of historical risk for human enteric viruses (when somatic coliphages exceed 50 PFU/100 mL), indicating the necessity for proof of viral log reductions across the treatment process. Future integration of this study’s catchment-specific data into a hybrid quantitative microbial risk assessment model could greatly assist in evaluating drinking water treatment works operation, ultimately contributing to the reduction of exposure to viral risk and regulatory non-compliance

Whistleblowers

The Chief Inspector of Drinking Water and Inspectors appointed under section 86(1) of the Water Industry Act 1991 became ‘prescribed persons’ and are part of the Prescribed Persons Order 2014 as amended (the Order). This means that any employees, ex-employees, or contractors can report information to the Inspectorate concerning wrongdoing (known as whistleblowing) and will be afforded certain protections under the Order and the Employment Rights Act 1996. In general terms, a person passing on information concerning wrongdoing (making a disclosure) should not suffer detriment or victimisation from their employers.

The type of disclosure that would typically qualify as a protected disclosure under the Order would be if it relates to the quality and sufficiency of water supplied by the water industry, and the security of network and information systems within the supply and distribution sector. This will likely be information pertaining to a breach or potential breach of the Water Supply (Water Quality) Regulations 2016 (as amended), the Network and Information Systems Regulations 2018 or the company not meeting its obligations relating to water quality or sufficiency or potentially committing an offence under the Water Industry Act 1991.

Any persons wishing to report a concern or potential concern regarding suspected or known wrongdoing which the Inspectorate can investigate should do so by contacting the Inspectorate’s enquiries line (dwi.enquiries@defra.gov.uk or 0330 041 6501). The Inspectorate treats all disclosures made by whistleblowers sensitively and seriously and follows up each disclosure with an appropriate investigation. The Inspectorate will protect the identity of any individual making an allegation wherever possible. However, in certain circumstances the Inspectorate may be required to reveal the identity, if required by law.

Eleven disclosures have been made to Inspectorate for the reporting period 1 April 2024 to 31 March 2025. Of the eleven disclosures made seven required further investigation. One disclosure was referred to an alternative body. Relevant action was taken from five of the disclosures made after these were investigated by the Inspectorate. This included the issuing of recommendations and legal instruments. 

The Inspectorate encourages water companies to have processes in place for employees and contractors to be encouraged and feel that they can speak up to report concerns around working practices which may impact on the company’s duties to meet its regulatory and statutory obligations for drinking water quality and network and information systems. To help foster an open and supportive culture the Inspectorate encourages companies to take initiatives such as a reporting line for water quality and network information system concerns (similar to which some companies have in place to report health and safety concerns) and to have a formal whistleblowing policy in place, which is also encouraged by the Department for Business and Trade who has published whistleblowing guidance for employer’s code of practice.

Working with stakeholders

The Inspectorate works with a wide range of external organisations, other regulators, government departments, professional bodies and academic institutions in the delivery of its strategic objectives.

Figure 38 Water Industry stakeholders

Defra

The Inspectorate is a business unit in Defra’s Floods and Water Directorate. As the independent regulator for drinking water quality, it is not directly responsible for development of policy, although the Chief Inspector has a statutory duty to report on quality matters to Welsh Ministers and advise of any regulatory changes required. The Inspectorate actively engages with Defra and Welsh Government officials on matters relating to water quality and sufficiency, resilience and water emergencies. Engagement with Defra during the year also included the area of water resources ensuring that water quality concerns are considered fully in the determination of options to meet future demand, and various matters relating to sufficiency, demand management and water saving initiatives.

Ofwat and innovation

The Inspectorate has monthly liaison meetings with Ofwat to share information on company performance. It has worked together with Ofwat to develop common performance measures, to ensure the regulators are aligned. Common performance measures are in place for two water quality metrics: water quality contacts and compliance with regulatory standards. Companies receive penalty fines if their CRI is worse than a set benchmark, based on industry average performance.

The Inspectorate works with Ofwat to support innovation within the sector, whilst ensuring consumers remain protected at all times.

RAPID

The Regulators’ Alliance for Progressing Infrastructure Development in Water (RAPID) was established to coordinate development and delivery of large-scale water resources infrastructure schemes, some of which will cross company boundaries, and improve resilience of supplies.

During 2024 the Inspectorate has continued to support RAPID by liaising with the Strategic Resource Options (SRO) sponsor companies, to ensure that all drinking water quality risks are being considered and appropriate mitigations identified as the schemes are progressed. This has included assessing the first ‘gate 3’ submission for the Hampshire water transfer and water recycling SRO which was submitted in July 2024, with the draft decisions published in November 2024 and the final decisions published in February 2025.

The Inspectorate has also met with the SRO teams to discuss the progression of the development of the monitoring plans which feed into the strategic water quality risk assessments and drinking water safety plan development, as the schemes head towards their ‘gate 3’ submissions, and in the later part of 2024 worked closely with RAPID to help shape the PR24 RAPID scheme submission and assessment process.

Regulators Pioneer Fund – StreamLine project

The Drinking Water Inspectorate is one of three regulators along with Ofwat and the Environment Agency who have set up StreamLine to make it easier for innovators to obtain advice

The Environment agency and Natural Resources Wales

The Inspectorate has been engaging with the Environment Agency on drinking water protected areas, and it has a data sharing agreement where it sends the raw water data it received from companies to the Environment Agency for river basin management plans. The Inspectorate uses the environmental surveillance data to inform its regulatory policy, for example, to identify and inform water companies about which PFAS to include in their sampling and catchment risk assessments. The Inspectorate is working with Natural Resources Wales to develop working agreements following the model in place with the Environment Agency.

European regulators

The European Network of Drinking Water Regulators (ENDWARE) meets twice a year, hosted by rotating members, to discuss matters concerning drinking water quality. Topics include substances of emerging significance, and compliance with standards. Differing approaches to monitoring, analysis, and mitigation are shared for learning and awareness of best practice. Research findings may also be shared for awareness.

UK Health Security Agency and Public Health Wales

The Inspectorate liaises with the Health Security Agency and Public Health Wales as required, to address emerging issues and to seek advice on toxicology.

Drinking Water safety – guidance to health and water professionals

Drinking water safety – guidance to health and water professionals The Inspectorate has provided guidance for healthcare professionals in England and Wales on drinking water safety, which provides information on public and private supplies, the role of local authorities and the use of restrictions such as boil water notices, to protect public health.

The World Health Organization

The Inspectorate has been redesignated as a World Health Organization (WHO) Collaborating Centre for Drinking-water Safety until 2026. (Ref UNK-232). This recognises the Inspectorate’s knowledge of implementing risk-based regulation in the field of drinking water supply, practically implementing the WHO water safety plan approach that was first promulgated as drinking water policy globally in 2004. An important function of our collaborating centre role is to provide support in the form of regulatory and technical knowledge through WHO organised workshops, training programmes, benchmarking projects, and research studies.

Consumer Council for Water

The Inspectorate shares and exchanges information with CCW on drinking water quality issues, with an emphasis on issues that directly affect consumers, through attending meetings and providing reports.

United Kingdom Accreditation Service

To maintain public confidence in drinking water sampling and analysis the Inspectorate collaborates with UKAS and other UK regulators (Drinking Water Quality Regulator for Scotland, and Department of Environment for Northern Ireland) to ensure that the sampling and analytical practices of water companies and the laboratories they use can be independently verified. In addition to meeting the requirements of ISO 17025, the Inspectorate and UKAS have published additional guidance for the water sector (Reference LAB 37), which makes specific requirements to ensure water companies meet their regulatory obligations.

Standing Committee of Analysts

The Standing Committee of Analysts comprises a series of working groups of experts in their fields, who provide guidance on methods of sampling and analysis for determining the quality of environmental matrices. Guidance is published as Blue Books within the series Methods for the Examination of Waters and Associated Materials. The guidance can be found on the SCA website: www.standingcommitteeofanalysts.co.uk.

The Inspectorate’s Chief Inspector is the current SCA strategic board chairman, which provides strategic direction for the organisation’s forward programme of work.

British Standards Institute

The Inspectorate assists and participates in the writing of British, European, and International standards that are associated to drinking water. This includes the analysis of drinking water, including quality control, drinking water products such as taps and thermostatic mixing valves, treatment chemicals and products, as well as general guidance standards such as temporary supplies.

Standardisation meetings may require attendance, but membership can be by email correspondence and comment. A committee meeting is generally held either annually or biannually.

Local authorities in England and Wales

The Inspectorate continues to support local authorities in their role as regulators of private water supplies by reviewing and updating technical briefs on implementing the Regulations where necessary, and producing topic focussed case studies and guidance as learning opportunities arise. The Inspectorate visited local authorities, to discuss challenges and developments in ways of working, and to see private supply types such as those used at temporary events. These visits help the Inspectorate to write its technical guidance, ensuring that guidance is practicable. The Inspectorate’s website has a dedicated area for private water supplies and the team maintain the technical briefs and resources made available to private water supply managers, users, and local authorities.

The Inspectorate is a member of the steering committee of the Water Health Partnership for Wales, and each year contributes to the Partnership’s annual conference by participating in exercises and delivering presentations. The Chief Inspector produces two separate reports on private water supplies in England and Wales, to inform ministers of their quality, and the impact of their regulation. The private water supplies team assess the data and information submitted by local authorities, including test results and risk assessment summaries to produce the statistics and disseminate messages and common learning

Supply chain

The UK chaired the joint management committee of the four Member States group (4MS) with meetings in London, Berlin, and Lisbon. The 4MS is a voluntary group of countries including the UK, France, Germany, and the Netherlands, which works together on procedures for approval of materials and products in contact with drinking water with the intention of reducing the testing burden placed on industry by different approval schemes. The group has agreed to take forward a twin track approach, exploring opportunities for mutual recognition of existing approvals alongside the work already in hand on full harmonisation.

The Inspectorate has also responded to enquiries from and engaged with trade bodies, including the industry consortium for products in contact with drinking water. It has held two meetings with WRAS and Water UK on 4MS issues.

The Inspectorate also liaised informally with various supply chain members and representative bodies on drinking water supply matters.

Water Safe

The Inspectorate has a six-monthly liaison meeting with Water Safe and works collaboratively on campaigns. This year, it shared information on compliance breaches attributable to domestic plumbing, to enable Water Safe to promote safe practices and encourage the use of suitably trained plumbers.

Water quality standards advisory group

The function of the Drinking Water Inspectorate (the Inspectorate) is to protect public health and maintain public confidence in drinking water in England and Wales. The Inspectorate holds water companies to account to ensure they supply safe and clean drinking water, now and for future generations.

The Chief Inspector of Drinking Water has an advisory duty to the Secretary of State under Section 86(a)(ii) of the Water Industry Act 1991. In his letter to the Minister of July 2022, the Chief Inspector recommended a review of the list of the water quality regulations to address emerging risks and other contaminants. Over time, additional risks to drinking water quality have emerged due to the use of industrial chemicals and plastics, and the impact of climate change. Legacy issues, such as lead in older properties, remain.

Throughout 2024 the Inspectorate facilitated meetings of a group of experts convened by the Chief Inspector to review and advise on changes to the water quality regulations. The expert advisory group considered the scientific evidence, including toxicology and potential occurrence in drinking water supplies, of a defined list of 15 parameters, which included lead and per- and polyfluoroalkyl substances (PFAS). The review considered the addition, removal, tightening and relaxation of parameters to protect public health. International regulatory approaches were considered when evaluating the most appropriate options.

The full report and its recommendations and published on our website – https://dwi-production-files.s3.eu-west-2.amazonaws.com/wp-content/uploads/2025/02/28110805/Recommendations-and-full-report-of-the-advisory-group-Dec-2024.pdf

WIRED – Water Innovation – Regulators Exploring Data

The Inspectorate engaged with Ofwat and the EA in a joint project funded by the regulators pioneer fund to explore the use of data within the three organisations and how we could potentially share data between us in a safe and controlled manner to gain new insights into water company behaviour.

The basis for this was four design sprints and a one-day hackathon to investigate what may be possible should all three regulators decide to invest further into the ideas generated.

Annex A – Number of tests carried out by companies

Numbers in brackets reflect the number of active works, reservoirs or zones operated by that company in the region in 2024. Some companies are permitted to carry out some tests on samples taken from supply points, rather than from consumers’ taps

Company	Water treatment works	Service reservoirs	Consumer taps	Number of tests per company	Target number of tests
ALE	0(0)	0(0)	248(1)	248	248
HDC	4,743(6)	15,472(82)	9733(25)	29,948	29,949
DWR	67,522(66)	80,977(328)	88,331(152)	236,830	236,863
Total				267,026	267,060

Sampling shortfalls

Water companies are required under regulation to take specific numbers of samples at their assets, the required number varies due to a number of factors, the Inspectorate assesses the shortfalls and discusses them with the company to arrive at an agreed position on the number of shortfalls the company had during the year.

Companies should expect greater scrutiny on their shortfalls in future reports as the Inspectorate is taking a greater interest in this area and will soon begin to track them more closely.

Company code	Agreed sampling shortfall
ALE	0
HDC	1
DWR	33
Total	34

Annex B – Compliance with standards

Microbiological compliance at water treatment works

Parameter	Current standard	Total number of Tests	Number of tests not meeting the standard	Number of tests not meeting the standard per company
Clostridium Perfringens (sulphite-reducing clostridia)	number/100 mL	600	0
E. coli	number/100 mL	12,108	0
Turbidity – indicator	NTU	12,093	0
Total coliforms	number/100 mL	12,108	2	DWR(2)

Microbiological compliance at service reservoirs

Parameter	Standard	Total number of tests	Number of tests not meeting the standard	Number of tests not meeting the standard per company
E. coli	0 number/100 mL	20,057	0
Total coliforms	0 number/100 mL	20,057	12	DWR(10) HDC(2)

Microbiological compliance at consumers’ taps (water supply zones)

Parameter	Standard	Total number of tests	Number of tests not meeting the standard	Number of tests not meeting the standard per company
Coliform bacteria (indicator)	0 number/100 mL	8,703	30	DWR(26) HDC(4)
E. coli	0 number/100 mL	8,703	1	DWR(1)
Enterococci	0 number/100 mL	753	0

Detection of E. coli and Enterococci at treatment works, service reservoirs and consumers’ taps, by company

Company	E. coli in water leaving treatment works	E. coli in water leaving service reservoirs	E. coli at consumers’ taps	Enterococci at consumers’ taps
ALE	0 – 0	0 – 0	0 – 12	0 – 4
DWR	0 – 11,166	0 – 16,189	1 – 8,067	0 – 638
HDC	0 – 942	0 – 3868	0 – 624	0 – 111

Chemical parameters

Parameter name	Number of tests	Number of tests not meeting the standard	Number of tests not meeting the standard per company
1,2-Dichloroethane (total)	466	0
Aluminium (total)	3,152	0
Ammonium (zone)	921	0
Antimony	755	0
Arsenic (total)	755	0
Benzene (total)	466	0
Benzo[a]Pyrene (total)	761	0
Boron	455	0
Bromate	583	0
Cadmium (total)	754	0
Chromium (total)	755	0
Colour	3,187	1	HDC(1)
Copper (total)	755	0
Cyanide (total)	462	0
Electrical conductivity	2,959	0
Fluoride (total)	462	0
Gross alpha	1	0
Gross beta	1	0
Hydrogen ion (pH) – indicator – zone	3,186	0
Iron (total)	3,155	13	HDC(1) DWR(12)
Lead (10)	755	1	DWR(1)
Manganese (total)	3,156	1	DWR(1)
Mercury (total)	465	0
Nickel (total)	755	2	DWR(1) HDC(1)
Nitrate (total)	756	0
Nitrite – consumers taps	755	0
Odour	3,183	4	HDC(1) DWR(3)
Pesticides (total by calculation)	704	0
Polycyclic aromatic hydrocarbons (total by calculation)	727	0
Residual disinfectant – free	8,746	0
Residual disinfectant – total	8,121	0
Selenium (total)	755	0
Sodium (total)	755	0
Sulphate	462	0
Taste (quantitative)	3,183	8	DWR(7) HDC(1)
Tetrachloromethane (total)	464	0
Trichloroethene & Tetrachloroethene – sum of 2 substances (total by calculation)	465	0
Trihalomethanes (total by calculation)	757	0
Tritium	1	0

Pesticide parameters

Parameter name	Standard	Total samples	Total failures	Detected pesticides
Individual Pesticides	0.1 µg/L	9,243	0
Total		9,243	0

Annex C – Compliance failures and events

Scoring compliance failures

Company	Site name	Parameter	Sample date	Assessment	CRI
DWR	Bretton works Final	Coliform bacteria	15/05/2024	Covered by Legal Instrument	0.377
DWR	Barry / Sully	Iron	25/03/2024	Covered by Legal Instrument	0.261
HDC	Saltney	Odour	30/08/2024	Suggestions made	0.357
HDC	Saltney	Taste	30/08/2024	Suggestions made	0.357
DWR	Conwy	Iron	12/07/2024	Covered by Legal Instrument	0.367
DWR	Abergavenny / Cwmtillery	Taste	24/04/2024	Covered by Legal Instrument	0.306
DWR	Abergavenny / Cwmtillery	Manganese	24/04/2024	Covered by Legal Instrument	0.306
DWR	Hereford Central / North	Iron	21/11/2024	Covered by Legal Instrument	0.338
DWR	Hereford Central / South	Iron	21/10/2024	Covered by Legal Instrument	0.167
DWR	Llyswen	Iron	13/12/2024	Covered by Legal Instrument	0.039
DWR	Llyswen	Iron	25/10/2024	Covered by Legal Instrument	0.039
HDC	Rhos	Iron	02/07/2024	Satisfactory investigation, did not identify cause	0.167
DWR	Holywell / Mold	Taste	05/07/2024	Suggestions made	0.162
DWR	Monmouth / Trellech	Iron	04/01/2024	Covered by Legal Instrument	0.058
DWR	Rassau / Sirhowy Valley	Taste	19/06/2024	Covered by Legal Instrument	0.155
DWR	Windmill Hill service reservoir	Coliform bacteria	19/09/2024	Covered by Legal Instrument	0.151
HDC	Penrhos service reservoir	Coliform bacteria	16/07/2024	Suggestions made	0.142
DWR	Tram Road service reservoir	Coliform bacteria	27/02/2024	Covered by Legal Instrument	0.115
DWR	Abergavenny / Cwmtillery	Taste	12/08/2024	Trivial	0.076
HDC	Brymbo High	Coliform bacteria (zone)	30/09/2024	Satisfactory investigation, did not identify cause	0.066
DWR	Newport	Iron	22/02/2024	Covered by Legal Instrument	0.245
DWR	Newport West	Iron	14/06/2024	Covered by Legal Instrument	0.184
DWR	Brandy Hill service reservoir	Coliform bacteria	20/08/2024	Covered by Legal Instrument	0.056
DWR	Malpas / Caerleon / Cwmbran	Coliform bacteria (zone)	11/12/2024	Satisfactory investigation, did not identify cause	0.053
DWR	Bontgoch	Odour	08/04/2024	Recommendations made	0.052
DWR	Bontgoch	Taste	08/04/2024	Recommendations made	0.052
DWR	Bontgoch	Odour	25/04/2024	Recommendations made	0.052
DWR	Bontgoch	Taste	25/04/2024	Recommendations made	0.052
DWR	Bontgoch	Odour	08/07/2024	Recommendations made	0.052
DWR	Bontgoch	Taste	08/07/2024	Recommendations made	0.052
DWR	Penderyn	Iron	10/04/2024	Covered by Legal Instrument	0.05
DWR	Bryngwyn / Portis	Coliform bacteria (zone)	05/12/2024	Satisfactory investigation, did not identify cause	0.04
DWR	Builth works Final	Coliform bacteria	20/03/2024	Covered by Legal Instrument	0.043
DWR	Penarth / Barry	Coliform bacteria (zone)	14/03/2024	Satisfactory investigation, did not identify cause	0.022
DWR	Port Talbot / Skewen	Iron	04/04/2024	Covered by Legal Instrument	0.157
DWR	Whitbourne	Iron	27/11/2024	Covered by Legal Instrument	0.059
DWR	Bodafon service reservoir	Coliform bacteria	07/08/2024	Covered by Legal Instrument	0.034
DWR	Penlan Goodwick service reservoir	Coliform bacteria	29/07/2024	Covered by Legal Instrument	0.015
DWR	Penparc service reservoir	Coliform bacteria	26/02/2024	Covered by Legal Instrument	0.013
DWR	Meifod service reservoir	Coliform bacteria	19/06/2024	Covered by Legal Instrument	0.01
DWR	Newlands service reservoir	Coliform bacteria	30/10/2024	Covered by Legal Instrument	0.008
HDC	Cefn Twlch service reservoir	Coliform bacteria	05/04/2024	Recommendations made	0.008
DWR	Hawarden service reservoir	Coliform bacteria	10/12/2024	Unlikely to Recur	0.006
DWR	Plas Talgarth service reservoir	Coliform bacteria	02/09/2024	Covered by Legal Instrument	0.002
DWR	Rhymney / Bargoed	Lead	04/12/2024	Unlikely to Recur	0.002
HDC	Concessionary Supplies	Colour	22/02/2024	Recommendations made	0.001
DWR	Pencoed / Bridgend Valleys	Coliform bacteria (zone)	01/03/2024	Unlikely to Recur	0.049

Events in 2024

Company	Event name	Cause of event	Final Assessment	ERI
HDC	Saltney Taste & Odour	Treatment failure upstream of final disinfection	4	240.065
DWR	Talybont works Taste and Odour	Raw water deterioration	4	94.471
DWR	Tynywaun works Turbidity	Structural failure – Treatment works	4	57.096
DWR	Glascoed Taste and Odour	Raw water deterioration	3	16.664
HDC	Newtown Lead Do Not Drink	Company communication pipe problem	4	15.03
DWR	Llanrumney Burst Main	Mains problem/ damage – Mains – Burst	3	5.972
DWR	Gilfach Fargoed Loss of Supply	Mains problem/ damage – Mains – Burst	4	4.599
DWR	Rhydlafar Burst Main	Mains problem/ damage – Mains – Burst	4	2.737
DWR	Abergavenny 3rd Party Damage	Mains problem/ damage – Mains – Damage by Third Party/Unknown	4	2.500
DWR	Pengarnddu Old service reservoir	Animalcules	1	2.090
DWR	St Asaph Do Not Drink	Ground Contamination / Spillage – Hydrocarbon	3	0.766
DWR	Llwynypia Quarry Loss of Supply	Mains problem/ damage – Mains – Damage by Third Party/Unknown	4	0.708
DWR	Abergavenny Boil Water Notice	Satisfactory investigation, did not identify root cause	4	0.175
HDC	Newtown Taste and Odour	Consumer’s distribution system	3	0.153
DWR	Strata Florida works Turbdity	Plant failure – Failure – Sensors or Meters	2	0.084
HDC	Brymbo Low Do Not Drink	Consumer’s distribution system	1	0.068
HDC	Llwyn Onn Gravity Do Not Drink	Satisfactory investigation, did not identify root cause	1	0.051
HDC	Newtown Do Not Drink Ingress	Mains problem/ damage – Mains – Burst	3	0.033
DWR	Penybont works High Turbidity	Other – Specify Below: Defective non return valve on pumping main between site and off site contact cum distribution storage tank caused depressuristaion of said main. This led to unapprehended turbidity at the inlet to the reservoir on recharge and final water turbidity spike above 1 NTU for approx 1 hour as a result.	4	0.032
HDC	Brymbo High Do Not Drink	Consumer’s distribution system	3	0.031
DWR	Capel Iwan Do Not Drink	Back Siphonage	3	0.018
DWR	Penybont works Turbidity	Mains problem/ damage – Mains – Burst	3	0.013
DWR	LLANNERCH-Y-MEDD, Do Not Drink	Cross Connection	1	0.011
DWR	Llangorse- Do Not Drink	Satisfactory investigation, did not identify root cause	1	0.010
HDC	Legacy T&O Do Not Drink	Satisfactory investigation, did not identify root cause	3	0.01
DWR	Barry Do Not Drink	Cross Connection	2	0.007
DWR	Bodorgan Boil Water Notice	Satisfactory investigation, did not identify root cause	4	0.004
DWR	Butetown Do Not Drink	Consumer’s distribution system	1	0.004
DWR	Morriston Do Not Drink	Consumer’s distribution system	3	0.003
DWR	Llangernyw Precautionary Boil Water Notice	Other – Specify Below: Suspected ingress into temporary overland main suspected following observation of submerged feed standpipe. Subsequent investigation identified a leaking seal on said standpipe, system under 50 m head positive pressure throughout and two sets of downstream samples returned satisfactory results.	1	0.003
DWR	Chepstow Do Not Drink	Mains problem/ damage – Mains – Damage by Third Party/Unknown	1	0.002
HDC	Llanidloes T&O	Satisfactory investigation, did not identify root cause	1	0.002
DWR	Llandysul Do Not Drink	Mains problem/ damage – Mains – Burst	1	0.001
DWR	Hereford Do Not Drink	Consumer’s distribution system	1	0.001
DWR	Grosmont Do Not Drink	Ground Contamination / Spillage – Hydrocarbon	3	0.001
DWR	Neath Do Not Drink	Consumer’s distribution system	3	0.001
DWR	Tredegar Do Not Drink	Ground Contamination / Spillage – Hydrocarbon	3	0.001
DWR	Llanelli Do Not Drink	Ground Contamination / Spillage – Hydrocarbon	4	0.001
DWR	Pontarddulais Do Not Drink	Satisfactory investigation, did not identify root cause	1	0.001
DWR	Blackwood Do Not Drink	Consumer’s distribution system	1	0.001
DWR	Dolwen Do Not Drink	Ground Contamination / Spillage – Hydrocarbon	2	0.000
DWR	Tonypandy Boil Water Notice	Consumer’s distribution system	1	0.000
DWR	Caernarfon Do Not Drink	Consumer’s distribution system	1	0.000
DWR	Drefach Do Not Drink	Consumer’s distribution system	1	0.000
DWR	Fairwater Do Not Drink	Consumer’s distribution system	1	0.000
DWR	Kington Do Not Drink	Consumer’s distribution system	2	0.000
DWR	Treharris Do Not Drink	Satisfactory investigation, did not identify root cause	1	0.000
DWR	Rhyl Do Not Drink	Consumer’s distribution system	1	0.000
DWR	Monmouth Do Not Drink	Consumer’s distribution system	1	0.000
DWR	Newport Do Not Drink	Consumer’s distribution system	1	0.000
DWR	Brecon Do Not Drink	Ground Contamination / Spillage – Hydrocarbon	1	0.000
DWR	Llandysul Do Not Drink	Ground Contamination / Spillage – Hydrocarbon	1	0.000
DWR	Narberth Do Not Drink	Ground Contamination / Spillage – Hydrocarbon	1	0.000
DWR	Holyhead Do Not Drink	Ground Contamination / Spillage – Hydrocarbon	1	0.000
DWR	Denbigh Do Not Drink	Consumer’s distribution system	1	0.000
DWR	Chepstow- Precautionary Do Not Drink	Discoloured water – cause unknown at present	1	0.000
DWR	Bridgend Boil Water Notice	Consumer’s distribution system	1	0.000

Public
Population supplied	3,300,180
Water supplied (L/day)	941,728,000
Treatment works	69
Service reservoirs	394
Water supply zones	103
Length of mains pipe (km)	30,543
Surface sources	259
Groundwater sources	40
Mixed water sources	1
Private
Population supplied	67,130
Water supplied (L/day)	110,242
Number of supplies	14,904
Number of local authorities with private supplies	22
Supplies without a risk assessment	11,671

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Glossary

Dedication

Introduction

Infographic – Industry statistics

Figure 1. Companies supplying water in Wales

Table 1. Key facts about public and private water supply arrangements in Wales

Table 2. Percentage of samples meeting the standards

Infographic – Compliance with the standards in 2024

Table 3. Number of tests carried out by companies in Wales

Figure 2. CRI scores for companies in Wales

Figure 3. Industry Compliance Risk Index

Figure 4. Wales Compliance Risk Index for 2024

Figure 5. Wales CRI score by parameter

Microbiological failures

Table 4. Microbiological tests – The number of tests performed and the number of tests not meeting the standard

Microbiological detections at works and service reservoirs

Table 5. Detection of E. coli and Enterococci at treatment works, service reservoirs and consumers’ taps

Service reservoirs and treated water tanks analysis

Figure 6. Compliance breaches at Dŵr Cymru Welsh Water service reservoirs and treatment works

Images 1, 2 and 3 Newlands service reservoir

Figure 7. Number of microbiological breaches in Wales zones

Chemical and physical parameters

Table 6. The number of tests performed and the number of tests not meeting the standard

Lead

Taste and odour

Figure 8. Taste and odour breaches in zones (including breaches located in England)

Images 4 and 5 Spider in sample bottle

Iron

Figure 9. Dŵr Cymru Welsh Water iron breaches

Water quality events infographic

Figure 10. Highest Event Risk Index

Figure 11. Wales ERI and median ERI

Table 7. Top 10 scoring events notified in 2024

Gilfach Fargoed Loss of Supply

Image 6 Fractured 24 inch main

Glascoed Taste and Odour

Rhydlafar Burst Main

Barry Do Not Drink

Tynywaun Turbidity

Abergavenny boil water notices

Saltney taste and odour

Newtown Lead

Llanrumney Burst Main

Abergavenny third-party-damage

Images 7 and 8 Valve damaged in field

Pengarnddu Old Service Reservoir

Images 9, 10, 11 and 12 Debris in service reservoir

Images 13 and 14 Skeletal remains of a dog

Morriston Do Not Drink

Image 15 Squirrel in hot water tank

St Asaph Do Not Drink

Images 16 and 17 Excavation of communication pipe and main and planters constructed with railway sleepers on grass verge.

Acceptability of water

Table 8. Water quality complaints in Wales, 2024

Discoloured water

Figure 12 Welsh company and industry discolouration rates 2015 to 2024

Figure 13 Rate of discolouration contacts by company in 2024 (excluding Isles of Scilly and inset companies)

Figure 14 Rate of discolouration contacts for Hafren Dyfrdwy (per 1,000 population)

Figure 15 Rate of discolouration contacts for Dŵr Cymru Welsh Water (per 1,000 population)

Taste and odour

Figure 16 Rate of taste and odour contacts in Wales

Events contacts

Figure 17 – 2024 Discolouration events in Wales by number of consumer contacts

Treated water tanks and service reservoirs

Figure 18 Dŵr Cymru Welsh Water tank inspections

Figure 19 Hafren Dyfrdwy tank inspections

Figure 20 Industry – tank assets at risk

Granular activated carbon management

Disinfection control

Drinking Water Safety Plan (DWSP) guidance

Audits

Portsmouth Water

Southern Water

Dŵr Cymru Welsh Water

Northumbrian Water

Risk Assessment Record (RAR) reporting and company breakdown of DWI categories

Table 9 RARI calculation

Figure 21 – DWI RAR categories applied across the industry – all stages

Figure 22 Percentage RAR categories for the whole industry at the treatment stage