- Drinking Water 2024 – Summary of the Chief Inspector’s report for drinking water in England
- Foreword
- Water supplies and testing
- Compliance with water quality standards
- Water quality events
- Asset health and service reservoir integrity
- Consumer contacts
- Water safety planning and risk assessment
- Perfluoroalkyl and polyfluoroalkyl substances (PFAS)
- Audit programme completed by the Inspectorate
- Enforcement, transformation and recommendations
- Lead in water
- Materials in contact with drinking water (Regulation 31)
- Security and Emergencies (SEMD)
- Network Information systems (NIS)
- Research publications
- Raw water data
- Whistleblowers
- Working with stakeholders
- Annex A – Number of tests carried out by companies
- Annex B – Compliance with standards
- Annex C – Compliance failures and events
Compliance with water quality standards
The percentage of compliance with the standards in the Water Supply (Water Quality) Regulations 2016 (as amended) is shown below, and details of all the failures are set out in Annex 3 by site type and by company.
| Parameter group | % Compliance (2dp) |
|---|---|
| Chemical parameters | 99.95% |
| Indicator parameters | 99.97% |
| Microbiological parameters All | 99.98% |
| Microbiological parameters (Reservoirs) | 99.96% |
| Microbiological parameters (Treatment works) | 99.98% |
| Pesticides | 100.00% |
| Overall | 99.97% |
The diagram below represents the quality of drinking water received by consumers, and the numbers and parameters which failed to meet the standards in 2024.
Figure 5 and Table 7 – 2024 compliance overview
Compliance with the drinking water standards is consistently high in England. Testing is designed to verify drinking water quality at practicable intervals at key supply system locations. However, scrutinising company water safety plans, audits and events reveal risks within drinking water supply systems which on investigation may require additional mitigation to reduce risks.
The Inspectorate has developed a series of risk indices to identify where companies should address risks to supplies. It uses the Compliance Risk Index (CRI) to measure the impact of a compliance failure on company performance, and the potential impact of those compliance 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 bar chart below shows the CRI for each company operating in England divided into site types, zones (consumer taps), water treatment works and service reservoirs.
Of all the compliance failures during 2024, 472 were related to consumer distribution systems.
CRI by company
The CRI is not a statutory measure; it does not remove the duty for a company to comply with each parametric value set out in the Regulations. However, as a risk-based metric, the objective is to incentivise the companies resource to focus on highest risk in a precautionary manner. It is shared with the financial regulator, Ofwat, as a common performance measure as an integrated regulatory strategy intended to promote improving water quality in the public interest. Whilst the Inspectorate does not accept any compliance failures as being acceptable, a CRI target of 2 has been set as the point from which financial penalties apply, ensuring outcomes remain risk focused, achievable and equitable when used as a water quality performance objective.
The median value for the industry in 2024 is 1.741 which reflects a change in risk-focus through regulatory activity when compared to 3.040 in 2023, 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 of companies and the regulatory action taken by the Inspectorate, since the issuing of notices in response to risk purposefully augments the measure creating a focus on areas of greatest need. Those companies in the top half reflect the ongoing strategic risks and the consequent increase in regulatory action. The overall CRI is comprised of figures representing performance of different parts of the water supply chain (treatment works, supply points, service reservoirs and zones). The data includes all regulatory failures, such as indicator parameters taken at treatment works, service reservoirs and consumer taps, and is used for the CRI calculation. The objective is to highlight all risks and all locations which require improvement.
Failures at water treatment works contribute the greatest amount to company CRI scores. They score highly because of the large population served reflecting the relative risk to the largest number of people. These sites are wholly within the companies’ control meaning that failures should be adequately mitigated and avoided.
Figure 6 and Table 8 – Company compliance risk index scores
The highest scoring parameter by a considerable majority is total coliforms which accounts for over half of the total CRI score on its own.
Figure 7 and table 9 – CRI scores by parameter
All compliance failures are assessed in line with the Inspectorate’s Enforcement policy: www.dwi.gov.uk/what-we-do/enforcement_policy
Learning from compliance failures
The following tables show all the compliance failures within the year, the full list is published within annex B.
| Parameter | Standard | Total number of tests | Number of tests not meeting the standard | Number of tests not meeting the standard per company | Percentage compliance (2 DP) |
|---|---|---|---|---|---|
| Clostridium Perfringens (sulphite-reducing clostridia) (confirmed) | 0 number/100 ml | 24,840 | 8 | UUT(2) BRL(1) NES(2) TMS(1) SVT(2) | 99.97% |
| Turbidity – indicator | 1 NTU | 171,438 | 19 | UUT(1) TMS(3) NES(2) SWB(1) BRL(2) YKS(1) SVT(3) ANH(2) PRT(1) ISC(1) SST(1) SRN(1) | 99.99% |
| E. coli (confirmed) | 0 number/100 ml | 171,591 | 3 | ANH(1) SRN(1) TMS(1) | 100.00% |
| Total coliforms (confirmed) | 0 number/100 ml | 171,598 | 80 | SWB(2) SRN(6) ANH(11) YKS(12) SEW(2) UUT(3) TMS(6) PRT(1) ISC(2) CAM(1) NES(7) BRL(1) SVT(18) WSX(3) SST(5) | 99.95% |
| Total | 539,467 | 110 |
Microbiological failures
E. coli
The detection of E.coli indicates faecal contamination and robust contingency plans must be in place to mitigate the impact of detections and provide protection, for the public, from water which may be considered unwholesome and potentially unfit. Throughout 2024 there was only three detections of E. coli in samples taken from treatment works from 171,591 tests carried out, from service reservoirs there were seven detections from 182,653 tests and from consumer properties there were 30 detections from 153,474 tests carried out. In total there were 40 E. coli detections in 2024, this is an improvement over the 41 in 2023.
Southern Water – Stanhope Lodge Worthing WTW – E. coli
In June 2024, three E. coli and 67 coliforms were detected at Southern Water’s Stanhope Lodge treatment works. The detection was also reported as a drinking water quality event. Stanhope Lodge is under notice SRN-3926 which covers risks associated with ingress/treatment failures leading to bacteriological detections. The company investigation did not identify any issues with structural integrity and did not identify any deficiencies with the operation of the disinfection system which is provided by UV. Pre and post UV samples taken on the same day that the failing sample was collected were clear of bacterial detections.
Resamples were taken from the compliance point as well as a downstream service reservoir and consumer properties, which all returned clear. A site inspection did identify that some improvements were needed such as the removal of the redundant gas injection lines and old main dose instrument sample line, capping of the Quadrina tapping and sealing of ducts in chambers. There had been no E. coli detected in the raw water in the lead up to the detection or in the previous three years.
The company conclusion was that the most likely cause was contamination of the sample. However, in the absence of any evidence to support this conclusion the company undertook enhanced monitoring for three months with no further detections reported. The company confirmed to the Inspectorate that the improvements identified during the site inspection had been completed onsite.
Anglian Water – Little Melton WTW – E. coli
Seven E. coli were found in a regulatory monitoring sample collected from the Anglian Water Little Melton treatment works on 09 April. Investigations found ingress into a reservoir at the works and remedial work to repair was undertaken.
Following a later repeat coliform detection in a sample collected on 16 June, the company installed temporary ultra-violet (UV) treatment.
The sampling investigation undertaken by the company for the second failure was inadequate with only one consumer sample taken, despite the works supplying a large population. Recommendations were made by the Inspectorate to re-brief teams responsible for arranging resampling surveys to ensure an appropriate investigation is undertaken to ensure that public health is not at risk.
Thames Water – Horton Kirby WTW – E. coli
In January 2024, E.coli was detected in a sample from Thames Water’s Horton Kirby works. Despite heavy rainfall at the time of the exceedance, the company’s investigation concluded that there had been no ingress to the treatment process.
However, the investigation reported that the sample tap at Horton Kirby is kept running continuously and that therefore the flame sterilisation of the tap, with the water running is poor practice. The company subsequently changed their sampling procedures to allow taps to be disinfected whilst running. The Inspectorate shall take further action to address this issue across the company to ensure that sampling procedures are in line with industry good practice and that samples are representative.
Coliforms
Testing for coliform bacteria gives reassurance that water entering supply was treated adequately to remove bacterial and viral pathogens. Repeated occurrences of coliform bacteria in samples from the same works in one year are thus of concern and require action to be taken. There were 80 coliform failures from 171,598 tests undertaken.
Equally, testing for coliform bacteria gives reassurance that the quality of water held in service reservoirs at strategic points in the distribution system is adequately maintained. The national standard requires that at least 95% of no less than 50 samples collected from each service reservoir throughout one year are clear of coliforms. From the 122 failures from 182,652 tests for coliform bacteria four reservoirs failed the 95% rule. Of these reservoirs Mynd and Chillies were not in service for the whole year and were taken out of service following the failures.
Severn Trent Braybrook reservoir was removed from service one cell at a time and ingress was identified and repaired in both cells.
| Company | Site name | Parameter | Samples taken | Samples failed | Percentage compliance (2 DP) |
|---|---|---|---|---|---|
| SEW | Chillies Reservoir Outlet 1 | Total coliforms (confirmed) | 1 | 1 | 0% |
| SVT | Mynd DSR | Total coliforms (confirmed) | 9 | 1 | 89.89% |
| SVT | Braybrook DSR combined Outlet | Total coliforms (confirmed) | 52 | 3 | 94.23% |
| YKS | Oughtershaw SRE | Total coliforms (confirmed) | 52 | 6 | 88.46% |
Yorkshire water – Oughtershaw reservoir – Coliform bacteria
A compliance sample taken from Oughtershaw service reservoir on 24 September 2024 was found to contain 122 coliform bacteria per 100ml. On 25 September 2024, a restriction of use boil water advice was provided to one property downstream of the asset in the K848 Oughtershaw district metered area in North Yorkshire and on 26 September 2024 boil water advice was provided to the remaining eight properties. In total, Oughtershaw service reservoir breached schedule 1 of the Regulations once for E.coli and six times for coliforms in 2024. Oughtershaw service reservoir was not fully bypassed and taken out of service until 4 March 2025. Microbiological water quality improved significantly thereafter, and the health protection advice was lifted at all properties on 13 March 2025. Restriction of use advice remained in place for consumers for 201 days.
Although the company’s investigation carried out extensive sampling surveys and found an NRV that was causing depressurisation in the inlet main early into the investigation, it was not until 9 December 2024 that the company carried out a walkover of the main and discovered an unmapped air valve. Satisfactory sample results were interspersed with detections of indicator organisms and therefore, the inconsistency in the company’s sample results further led to a delay between interventions carried out. The company’s investigation would have benefited from a more robust application of procedures, processes, and root cause analysis to fully assess the potential risks associated with both existing and legacy infrastructure.
The Inspectorate recommended that the company review its procedures to ensure investigations are initiated and carried out promptly, in order to mitigate the risk of future regulatory breaches. In addition, suggestions were made for the company to review its asset records to support effective incident management and ensure that system-wide learning is captured and applied following this event.
The public health implications from this lack of reservoir inspections and lack of records for their air valves could have been severe and in this instance the company were lucky and got away with it.
The company plan to create a new Continuous Improvement team which will be tasked with investigating the root cause of water quality failures. The company also has a “red-lining” process by which asset records will be updated as and when a physical discrepancy is discovered in the network or other Company assets. Companies should take learning from this event to ensure that investigations are initiated early on to prevent prolonged risks to public health and extended consumer disruption. Prompt root cause analysis and asset assessment must be standard when microbial breaches occur and robust processes are needed to assess risks associated with legacy infrastructure.
Severn Trent Water – Strensham WTW – Coliform bacteria
The compliance samples from Severn Trent Waters Strensham treatment works reported one coliform per 100 ml on 27 and 28 Feb, with three coliforms per 100 ml also reported for 2 March. Operational samples prior to the detection reported two post-disinfection samples which contained one coliform per litre.
The company concluded the operation of the treatment works to be satisfactory prior to exceedance, compliance with disinfection criteria had been maintained throughout. No changes in raw water quality had been observed. There was a potential concern identified in an ROV inspection of the north balance tank. However, the tank subsequently passed the flood test, which looks for signs of active ingress.
A potential ingress risk was identified in the high lift pump sump tank due to a leak on a pumped main within the pumphouse building causing water to collect in the cavity space of the sump tank wall. The leak was repaired on 13 March with the potential ingress risk also removed, however there were a further six post-disinfection detections between 13 and 25 March of one coliform per litre.
United Utilities – Oswestry WTW – Coliform bacteria
38 coliforms in 100ml were detected in a sample from United Utilities Oswestry treatment works on 16 August 2024.
The company had been carrying out significant valving operations between the 13 and 15 August 2024 to allow the installation of outlet pipework on the new rapid gravity filters. The work involved opening a valve that has been closed since 2020, which splits the slow sand filters into two streams. The company had written an appropriate method statement and undertaken a risk assessment for the work to demonstrate that a calm networks approach was implemented, and additional turbidity monitoring was put in place.
In addition to valving, the work also necessitated diverting the entire works flow via stream one, which involved closing the outlets on the stream two slow sand filters and bringing them back online via stream one. Three slow sand filters were returned to service, via stream one. After the coliform exceedance was reported to the company, a defect was identified with one of the slow sand filters. The filter was removed from supply and an investigation revealed that a tile on the filter floor had moved out of place, this would have allowed water to bypass the treatment stage. This was subsequently rectified and returned to supply. The company concluded that this could not be ruled out as the cause of the coliform detection.
Trends provided by the company further revealed that although the company could demonstrate the chlorine contact time was satisfactory and that water had been adequately disinfected prior to and on the day of the exceedance, trends from the stream one UV reactors show that there were outages on the system between 09:30 to 09:55 and 10:35 to 10:45 where no UV disinfection would have been occurring. Follow up information from the company confirmed that between May and October 2024, there were UV outages on 22 occasions at Oswestry works. The disinfection policy states that the UV dose is precautionary, however, because the UV reactors were installed to provide inactivation of Cryptosporidium, the Inspectorate concluded that regulation 26 applied to this process, therefore, failure of this system cannot be ruled out as the cause of the coliform detection.
The Inspectorate concluded that the company had not complied with the requirement to optimise existing treatment processes to ensure continuous compliance and had not satisfactorily implemented the requirement to complete the installation and commissioning of validated UV disinfection treatment capable of treating full works flow in notice UUT-2020-00003. The installed systems were capable of significantly reducing the bacteria risk buy by operating the system in the manner they did the company were not complying with the regulations which are in place to protect public health.
As a result, the company were issued with a regulation 28(6) intention to vary a notice and a further recommendation to review the trigger response times for UV outages to ensure that UV dosage was maintained at Oswestry.
Cambridge Water – Bluntisham Reservoir – Coliform Bacteria
Coliform detection at Bluntisham Reservoir 2. No root cause was identified, however the company have not yet completed the inspection and flood test of the reservoir, or the sample line audit. The company took the reservoir cell out of service to investigate on the same day the result was reported, and any required remedial works identified during the inspections will be completed prior to returning the reservoir to supply. Recommendations made regarding compliance sampling at the reservoir and the implementation of the company’s reservoir inspection program.
Affinity Water – Harefield reservoir 3 West – Coliform bacteria
A sample collected from Harefield Reservoir 3 West recorded a coliform bacteria result of 1/100mL in a sample collected on 19 March 2024. The company determined that the cause of the original failure was lower than normal turnover within the reservoir due to an increase in the water storage level. The company increased the reservoir water level as a precautionary measure should there be mains damage from HS2 work in the vicinity of another company main. The company was aware of the water quality risks associated with increasing water levels in the reservoir and subsequently reducing turnover.
This reservoir recorded five previous coliform detections in 2017-18. To satisfy the recommendation made in 2018 concerning turnover, the company operated the reservoir between 2018-2023 with either the East or the West cell in supply.
The company must consider and mitigate all risks associated with the supply of water – covering both sufficiency and quality matters. The company knowingly increased the risk of coliform detection at this reservoir by increasing the water level without the introduction of some appropriate mitigation. Indeed, the company determined that the cause of the coliform bacteria detection was lower than normal turnover due to the increased water storage level. It is not appropriate for a company to take actions and decisions that increase the likelihood of a coliform detection at any of its assets.
The risk assessment reports do not include turnover or water age as being hazardous events. The Inspectorate has now recommended turnover is a hazardous event and the risk assessment is resubmitted to the Inspectorate.
The company had a capital project for resilience to install booster pumps at this site to improve turnover. The project was due to be operational by August 2024. The capital scheme was completed and commissioned in February 2025 and the booster pumps are in use. The pumps are not yet operating at full capacity, and the company has kept one of the two reservoirs out of supply to ensure adequate turnover.
Turbidity
Turbidity is a measure of how much light can pass through water and indicates the cloudiness of water. Turbidity maybe caused by either inorganic or organic particles suspended in the water. At a treatment works, turbidity is an important critical control in relation to determining whether raw water has been adequately prepared for disinfection. The turbidity standard at treatment works is 1NTU. There were 19 failures of this standard from 171,438 tests performed in England. Two of the key failures are reported on below:
South Staffs Water – Seedy Mill WTW – Turbidity
Resamples collected in response to the turbidity failure at Seedy Mill works were satisfactory. The original sample was found to contain elevated levels of iron, manganese and aluminium. The treatment works had been operating satisfactorily and there had been no identified issues with sample collection or the laboratory analysis.
Black particles were observed in net samples placed over the tap on the final water compliance point, which were composed of higher-than-normal levels of iron, manganese and aluminium.
Further investigations identified the turbidity breach to be related to enabling works (valve operations) to isolate the North and South pre-suction and suction tanks, which were due for their internal inspections.
Northumbrian, Essex & Suffolk water – Lartington WTW – Turbidity
A regulatory sample taken from Lartington treatment works final water sample point returned a turbidity of 1.3 NTU. Further analysis of this sample returned an iron concentration of 890 µg/L, and an aluminium concentration of 430 µg/L, and also elevated concentrations of copper (95 µg/L). Resamples and related samples were taken from downstream service reservoirs which returned satisfactory results. The following weekly regulatory sample returned a turbidity result of >0.2 NTU and did not contain elevated concentrations of iron or aluminium. An audit was carried out on the regulatory sample tap and found that the connection onto the outlet main would draw water from the outside of the main, not the centre.
On 3 January 2024 the works experienced multiple communication issues with outstations. Ferric coagulant dosing was put into manual to ensure continuous dosing, however when the ferric pumps switched over, the standby pump started up at a higher pump speed. The resulting overdosing of ferric caused a peak over 100 mg/L of iron in the final water, the pre contact tank turbidity reached 0.3 NTU.
A recommendation was against the sample point, requiring a review of all works final sample points following exceedances at Wooler, Mosswood and Lartington treatment works. Condition of sample points causing compliance failures is a recurring issue within the water industry and something that is completely within the control of the water companies to affect certainly given the financial implications of failures as they affect the CRI scores.
Chemical failures
The table below shows all the chemical failures during 2024, the full list of all chemical parameters sampled in included within annex B.
| Parameter name | Standard | Total number of tests | Tests not meeting the standard | Tests not meeting the standard per company | Percentage compliance (3 DP) |
|---|---|---|---|---|---|
| Benzo[a]Pyrene (total) | 0.01 µg/L | 13,174 | 2 | TMS(1) IWN(1) | 99.985% |
| Polycyclic aromatic hydrocarbons (total by calculation) | 0.1 µg/L | 13,452 | 1 | TMS(1) | 99.993% |
| Aluminium | 200 µg/L Al | 51,095 | 18 | NES(3) YKS(1) SRN(1) BRL(2) SST(1) UUT(7) AFW(3) | 99.965% |
| Iron | 200 µg/L Fe | 51,617 | 82 | SST(1) TMS(5) SRN(3) UUT(19) SEW(2) ANH(3) YKS(16) AFW(1) SWB(6) NES(10) WSX(1) BRL(2) SVT(13) | 99.841% |
| Manganese | 50 µg/L Mn | 51,465 | 11 | SEW(1) YKS(2) NES(1) SVT(1) UUT(6) | 99.979% |
| Nickel | 20 µg/L Ni | 13,401 | 70 | IWN(5) YKS(3) SES(3) NES(3) TMS(6) SEW(4) AFW(2) LNW(2) SRN(8) BRL(4) UUT(5) ESP(11) WSX(1) ANH(2) SVT(11) | 99.478% |
| Lead | 10 µg/L Pb | 13,410 | 53 | SRN(2) YKS(4) UUT(8) BRL(1) WSX(1) AFW(2) NES(2) ANH(3) SVT(8) TMS(22) | 99.605% |
| Gross alpha | 0.1 Bq/L | 750 | 13 | ANH(1) ESP(4) IWN(8) | 98.267% |
| Odour | Acceptable to consumers and no abnormal change | 56,028 | 68 | UUT(6) SVT(5) SEW(3) NES(16) SST(3) WSX(1) BRL(2) CAM(1) LNW(1) SRN(6) SWB(2) YKS(7) AFW(4) ANH(11) | 99.879% |
| Taste (quantitative) | Acceptable to consumers and no abnormal change | 55,887 | 55 | SRN(5) NES(12) ALB(1) YKS(12) SWB(1) UUT(5) ANH(5) AFW(1) ISC(3) SVT(3) WSX(3) BRL(3) IWN(1) PRT(1) | 99.902% |
| Copper | 2 mg/L Cu | 13,400 | 5 | SRN(1) AFW(1) BRL(1) TMS(2) | 99.963% |
| Sodium | 200 mg/L Na | 13,397 | 1 | AFW(1) | 99.993% |
| Ammonium (zone) | 0.5 mg/L NH₄ | 39,982 | 1 | TMS(1) | 99.997% |
| Hydrogen ion (pH) – zone | 6.5 – 9.5 pH Value | 55,431 | 3 | UUT(1) ISC(1) SWB(1) | 99.995% |
| Total | 441,489 | 383 |
From samples in zones, iron, manganese and aluminium contribute 29% of all the chemical failures. This emphasises the impact the potential causes of discolouration that can affect consumers. Iron and aluminium are the two base chemicals used in the treatment of surface water during the primary coagulation stage. They are of high importance as part of a multi barrier approach to treatment as they remove the bulk of particulate matter from water, however their use should be tightly controlled to ensure that no excessive carryover of either chemical occurs. Should this occur then the company risks ‘seeding’ their distribution network with particles which can build up over time and should any rapid flow changes occur then this could result in a downstream discolouration affecting a large number of consumers.
Taste & Odour
Albion water – Rissington – Taste
In July 2024 an Albion water sample from one of their zones reported positive for a taste result. The company concluded this was associated with the consumers tap. However, upon investigation by the Inspectorate it was found that the company had not conducted any investigation into the breach.
No investigational samples were collected, a fittings inspection was not carried out, upstream assets were not investigated and inappropriate advice was provided to the consumer.
The Inspectorate has taken this lack of action by the company very seriously and has raised recommendations regarding procedures, investigations, and provision of information. A follow up meeting with the company also took place to discuss expectations around reporting, investigation and safeguarding public health.
Nickel
High concentrations of nickel in tap water can cause skin irritation (allergic contact dermatitis). Nickel represents 18% of all chemical failures, this is primarily a consumer distribution system issue and commonly associated with newly installed taps which can be seen by the high number of failures from the inset companies IWN (5), LNW (2) and ESP (11) relative to their population size. Nickel may be present in coatings on modern tap fittings which are widely available, so can occasionally leach into water whilst it in contact with the fitting and are often the cause of failures in this area.
Advice should be offered by companies to consumers where these failures occur and consumers can help themselves by flushing their taps following any periods of stagnation. If you need to replace a tap or fitting, we recommend that you employ a qualified plumber to carry out any plumbing work. The Water Regulations Advisory Scheme provides information about accredited WaterSafe plumbers and approved fittings on its website.
Copper
Copper is in regular use throughout the country as a plumbing metal within the domestic, commercial and industrial sectors, the chemical properties of copper are excellent in this application as it is easy to use and has an inbuild level of microbial resistance. Failures of copper are rare, however the 5 exceedances in 2024 are noticeably higher that in other years.
Where failures do occur this is normally related to the installation of new pipework and/or low turnover. In many cases the copper was also associated with a high level of lead where pipework was identified as being galvanised. In those situations the company can undertake a water fittings inspection to identify if there are any issues, where the communication pipe is identified as being the cause the company is required to replace this
Sodium
Sodium failures are normally associated with water softener installations. Water softeners work by removing minerals like calcium and magnesium from your water supply through a process called ion exchange, effectively softening the water. This process involves using a resin bed coated with sodium ions. When hard water passes through the resin, the calcium and magnesium ions are attracted to the resin beads, while sodium ions are released into the water, thus softening it. Both calcium and magnesium are essential minerals and beneficial to human health in several respects. Inadequate intake of either nutrient can result in adverse health consequences.
A water company sampler should be checking with the consumer if a softening system is present, if there is a system they should avoid sampling from the softened tap as this is not representative of the mains supply. For the single failure which occurred for Affinity water, the sampler was directed to what was supposed to be an unsoftened tap
As far as consumers are concerned if you do install a water softener, it is very important that you make sure that it is correctly installed, and you do not soften the water to the tap in your kitchen which is used for drinking and cooking. This is because most water softeners work by replacing the hardness with sodium. Too much sodium can be a problem for premature babies because their kidneys are not good at filtering it out of the blood, and for people who are on a low sodium (low salt) diet. Artificially softened water may also be aggressive to plumbing causing leaching of copper and lead.
When purchasing a water softener, we advise that you buy it from a reputable supplier. It should be installed only by a qualified plumber who is a member of a recognised trade association, such as the Institute of Plumbing. We also advise that you consider putting in place a maintenance contract to ensure the softener continues to operate correctly and does not become a hygiene hazard.
Benzo (a) pyrene
Independent Water Networks Limited detected a Benzo (a) pyrene breach in its Tendring underground zone in January. Repeat samples at the property and investigation samples from neighbouring properties did not detect Benzo (a) pyrene above the limit of quantification. The company determined that the likely source was from the breakdown of coal tar lining of older cast iron mains within the bulk supply company network. The bulk supplier confirmed the presence of older mains upstream of the company’s water supply zone.
Fluoranthene was detected in all the samples collected as part of the investigation. Therefore, the Inspectorate did not concur with the company view that the failure is unlikely to recur.
The Inspectorate made recommendations associated with regard to the monitoring protocols the company had in place and failing to review the risk assessment for PAH related parameters in this zone in a timely manner
In July, there was an exceedance of the Benzo (a) pyrene standard in Thames Water’s Epping Forest zone, the cause was related to the temporary mobilisation of mains material as the result of a local burst main, investigatory results confirmed elevated PAH results nearby in the vicinity of the burst. There are coal-tar lined mains within the area and this risk had already been identified by the company and the Inspectorate had already issued a regulation 28 notice to address the risk. Following the repair of the main and the return to the usual supply arrangements within the area sample results returned below the regulatory standard.
Pesticide failures
| Pesticide name | Standard | Total samples | Total failures | Comments |
|---|---|---|---|---|
| Aldrin | 0.1 µg/L | 3,732 | 1 | LNW(1) |
| Propyzamide | 0.1 µg/L | 5,128 | 3 | UUT(1) SVT(2) |
| Dieldrin | 0.1 µg/L | 4,329 | 1 | LNW(1) |
| Bentazone | 0.1 µg/L | 5,294 | 2 | TMS(2) |
| Total | 18,483 | 7 |
During 2024 there were 7 failures for pesticides from 18,483 samples taken, the overall compliance rate to 3dp is 99.997%. Failures of the pesticide standard have reduced year-on-year since 2014 partly due to catchment management initiatives and the associated undertakings by companies as well as continuing improvements in
treatment such as the use of granular activated carbon among other technologies.
Some pesticides, whilst not impossible to remove by treatment, are difficult, expensive and problematical with available technology. The strategy for companies has therefore been to work with stakeholders in the environment to promote catchment management and to improve source water. Source water is subject to even the smallest changes in the environment which can have a profound impact on drinking water and companies will need to remain vigilant in their respective areas .
Propyzamide
The United Utilities failure investigation concluded that the exceedance of 0.153µg/l was caused by the application of propyzamide to already saturated land adjacent to the River Dee, following which there was a period of heavy rain in early February 2024, that subsequently washed the propyzamide in to the River Dee.
The company have put several actions in place to prevent a reoccurrence including established a working group to review propyzamide risk on the River Dee catchment, engaged with the main manufacturer of products that contain propyzamide for technical support and engaged with the landowner who advised they would not consider growing oil seed rape on the land for the next three years.
Severn Trent water had two failures from their Wolverhampton zone in 2024 in the areas supplied by the bulk import from South Staffs Water’s Hampton Loade WTW are a result of treatment deficiencies at the supplying treatment works. Upgrades to the treatment works in the near future will allow changes to the filtration at the works which should ensure more effective pesticide removal.
Aldrin and Dieldrin
Both of the failures from Leep networks water are associated with a laboratory problem and repeated AQC failures meaning that there was insufficient sample to fully complete the analysis, which resulted in the company’s contracted laboratory reporting a result with a raised LOD, which was higher than the PCV for these pesticides. The laboratory was unable to confirm the exact levels of the pesticides, only that it was <0.032µg/l for aldrin and <0.036 µg/l for dieldrin.
The company’s current process with requires any anomalies to be raised with the company’s contract manager, however the issues with the AQC failures resulting in insufficient sample were not reported to the company prior to the release of the analytical data. Further to this, as the results were reported with a less than ‘<’ which preceded the result, this did not flag on the system as a failure.
When the laboratory released these sample results to the company, commentary relating to the AQC failures was added to the analytical report however these were not identified by the company. As such, the sample results were not recognised as breaches and therefore compliance breach reports were not submitted to the Inspectorate for the October compliance submission.
These errors were subsequently identified by the Inspectorate and the company submitted a failure report.
Bentazone
Two failures within the Thames water Clatford zone where high levels of Bentazone were found in the raw water and the treatment works had insufficient treatment systems in place to be able to remove it, the investigation did not identify a source and the issue could be historic as no farmers were found to be using Bentazone. Concentrations appear to correlate well with ground water levels being high in Winter / Spring indicating that there could be soil contamination which is affected by rain and high levels of ground water.
The Inspectorate had previously issued a notice which is in place and is due to be completed in 2028.