- 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
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). During 2024 the team assessed 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 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 issued guidance where necessary to help companies in their approach to compliance with the regulations regarding risk assessment.
Per and polyfluoroalkyl substances (PFAS)
The Inspectorate has long been aware of challenges related to PFAS, issuing guidance on two specific PFAS, PFOS and PFOA over a decade ago. As the prevalence of PFAS within the environment and scientific advances in understanding their nature and detecting them in water samples has evolved, the Inspectorate has produced further guidance for water companies on the steps required to address PFAS risks. The Inspectorate expects water companies to adopt a tiered approach to risk assessment, monitoring, and management of PFAS concentrations.
PFAS guidance was consolidated and issued in August 2024. It included a requirement to implement a risk reduction strategy to progressively reduce PFAS concentrations at tier 2 as well as tier 3 sites, the application of tiers to final water and raw water where there is no treatment in place, monitoring and reporting of the compound 6:2 FTAB (6:2 fluorotelomer sulphonamide alkyl betaine) added to the list of PFAS parameters and reporting of the ‘Sum of PFAS’.
The latter two requirements were implemented on 1 January 2025, with the expectations of the PFAS guidance extended to companies holding New Appointments and Variations (NAVs). These companies should exchange information and data and also have a forward-looking PFAS strategy. All PFAS chemicals of interest were listed in the Annex C of the Information Direction. It is incumbent on companies to notify the Inspectorate should PFAS chemicals not listed be identified at concentrations above tier 1. The guidance was further updated in March 2025 to provide clarity on company reporting of tier 3 events.
A PFAS and catchment risk assessment working group was hosted by Severn Trent Water at their training academy in Coventry in October. This was attended by industry and regulatory delegates including the Inspectorate. The Inspectorate delivered a presentation on the regulatory perspective of risk assessment in catchments regarding PFAS which reiterated the PFAS guidance issued in August with Information Letter 03/2024. The use of hazardous events to describe potential contribution of PFAS from the catchment within risk assessments was discussed along with the importance of internal and external stakeholder engagement in understanding PFAS risk.
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 the 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 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 Information Direction, published in July 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 issued to review regulation 27 risk assessments and regulation 28 reporting. The new DWSP guidance should address some of the inconsistencies we have identified throughout the year and improve the quality of the information provided.
During 2024, the risk assessment team carried out four audits on the drinking water safety plans at Portsmouth Water, Southern Water, Dŵr Cymru 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 continues to work on surface water catchment risk assessments required to satisfy the requirements of the notice.
Southern Water – The Risk Assessment team undertook a two day audit which comprised a day to assess the company’s DWSP, and a 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 – 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, a number of 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 carried out, all of which are fundamental elements of a DWSP. Other areas identified as needing improvements 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 has issued the company with ‘Minded to Enforce’ letters covering the required actions for delivery under legal instruments yet to be determined.
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 any problems were easily resolved with good communication from companies and input from the Inspectorate’s Data Team.
Risk assessment record data is submitted using the DWI categories shown with definitions in the table below. 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.
| 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 below shows that over half of the industry identified risks to water quality have verified mitigation in place.
Figure 13 and Table 23 – The percentage of RAR categories across the industry at the treatment stage for England and Wales.
Risk assessment record categories F, G, I and X have been excluded from the above chart. 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 in a section 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
The 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 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 DWI 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 14 and Table 24 – Top 10 current identified risks to the whole industry
The top 10 hazards represent 39% of all hazards included in RARI calculations.
Figure 15 & Table 25 – Company average RARI scores for 2023 and 2024 are shown below. The median RARI value is 7.78.
Figure 16 & Table 26 – Company average RARI scores for 2023 and 2024 are shown below – graph 2
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 issued to 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 Information Direction 2025 by February 2027.
AMP 7 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.
Whole Industry AMP7 RARI Table
| Company | 2020 RARI | 2021 RARI | 2022 RARI | 2023 RARI | 2024 RARI |
|---|---|---|---|---|---|
| ISC | – | – | 519.561 | 643.51 | 2110.3 |
| ESP | – | – | 190.06 | 38.684 | 184.58 |
| VWP | – | – | 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 | – | – | 0.07 | 0.07 | 0.07 |
Portsmouth Water and Hafren Dyfrdwy RARI trends are shown on the primary axis in the graph below [Figure 17] for scale alongside companies with similar trends. 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.
Figure 17 & Table 28 – Companies with RARI scores >10 at the end of 2024 are shown below.
Companies shown in the graphs below show similar increases in RARI scores at the start of AMP7 to those in Figure 17 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.
Figure 18 & Table 29 – Companies with RARI scores <10 at the end of 2024 are shown below.
NAV RARI score changes across AMP7 are shown 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 19 and Table 30 – AMP7 RARI trends for NAV companies
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.
The graph below shows that the highest proportions of company perceived future risks are from abstraction and storage stages.
Figure 20 and Table 31 – Top 10 future risks
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.