- Drinking Water 2025 – Summary of the Chief Inspector’s report for drinking water in Wales
- Foreword
- Introduction
- Water supplies and testing
- Compliance with standards
- Learning from compliance failures
- Learning from events
- Consumer contacts
- Asset health
- Water safety planning and risk assessment
- Poly and perfluoroalkyl substances (PFAS)
- Audit programme
- Recommendations
- Enforcement
- Security and Emergency Measures Direction - SEMD
- Network and Information Systems - NIS
- Materials in contact with drinking water (Regulation 31)
- Research publications
- Whistleblowers
- Working with stakeholders
Compliance with standards
The percentage compliance with the standards in the Water Supply (Water Quality) Regulations 2018 (‘the Regulations’) is shown in Table 3 below.
| Parameter Group | % Compliance |
|---|---|
| Chemical Parameters | 99.93 |
| Indicator Parameters | 99.98 |
| Microbiological Parameters | 99.99 |
| Microbiological Parameters (Reservoirs) | 99.97 |
| Microbiological Parameters (Treatment works) | 99.99 |
| Pesticides | 100 |
| Overall | 99.97 |
Figure 3 – Compliance with the standards in 2025
Shortfalls
The number of samples required to be taken is specified in the regulations. In 2025 companies reported the following sampling shortfalls in table 4.
| Company | Number of tests per company | Target number of tests | Number of sample shortfalls | Shortfall |
|---|---|---|---|---|
| Albion Eco | 248 | 248 | 0 | 0% |
| Hafren Dyfrdwy | 29,949 | 29,949 | 0 | 0% |
| Dŵr Cymru Welsh Water | 263,830 | 264,319 | 489 | 0.19% |
| Wales overall | 294,027 | 294,516 | 489 |
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.
Advances in mapping technology have identified instances where samples were taken outside the correct zones. Where such issues were evidenced, the relevant companies were contacted and the affected samples were removed from the dataset on the basis that they were unrepresentative. In many cases, companies were also required to report these occurrences as formal events.
The Inspectorate will continue to scrutinise both the locations and frequency of sampling to ensure companies comply with regulatory requirements, including taking the correct number of samples at appropriate locations.
In parallel, the Inspectorate is reviewing the shortfall process, with the aim of introducing monthly automated updates to companies on their monitoring performance. This is intended to support sufficient, regular, and random sampling in line with regulatory expectations.
Compliance with the monitoring requirements set out in the Regulations remains consistently high in Wales. These requirements include the prescribed concentrations or values for parameters in drinking water, together with the required sampling frequencies and locations. This end-point verification provides broad assurance that supply systems are delivering water to consumers that meets regulatory requirements at the time and place sampled. However, company risk assessments continue to identify risks that are not fully controlled or mitigated. Where these risks are realised, they may result in a water quality impact, including a compliance failure or a notifiable event.
Where risks are realised, they may result in a compliance failure or a water quality event. The Inspectorate uses these outcomes to inform indices that assess the impact of failures and events, and the effectiveness of company actions to remediate risks and prevent recurrence. The Compliance Risk Index (CRI) measures the impact of compliance failures and their potential consequence for consumers. It is designed primarily as a regulatory tool to support proportionate scrutiny and ensure attention is directed to areas of greatest relative risk. Figure 4 shows company CRI performance.
In 2025, the Compliance Risk Index (CRI) for Wales remained elevated when compared with the wider industry. The three largest contributors to the Wales CRI score were coliform detections at Dŵr Cymru Welsh Water’s Court Farm and Bretton works, and a turbidity failure at Hafren Dyfrdwy’s Llandinam works. Dŵr Cymru Welsh Water recorded the highest CRI score in the industry at 7.1, while Hafren Dyfrdwy ranked 15th with a score of 1.253.
In total, Wales recorded three coliform breaches at treatment works and 18 coliform breaches and two Escherichia coli (E. Coli) breaches at service reservoirs in 2025. Eight of these breaches were covered by a Dŵr Cymru Welsh Water legal instrument, increasing the CRI score through the application of the relevant multiplication factor. Delivery of these legal instruments should secure improvements that reduce the likelihood of these risks recurring; once closed, the associated multiplication factor will no longer apply to the CRI score. In the context of increased regulatory scrutiny during transformation, the CRI for Wales is expected to remain elevated in the near term. This does not indicate a deterioration in drinking water quality, which remains excellent, but reinforces the importance of long-term strategic improvements to protect future supplies and manage risk.
Figure 2 shows variability in CRI for both Dŵr Cymru Welsh Water and Hafren Dyfrdwy since 2020, rather than a consistent trend.
Figure 4 – CRI scores for companies in Wales – last 5 years
Figure 5 shows the CRI for each company operating in England and Wales, broken down by site type: water treatment works, supply points, service reservoirs and zones.
Figure 5 – Industry Compliance Risk Index
The Compliance Risk Index (CRI) is not a statutory measure and does not override companies’ obligations to comply with prescribed concentrations or values under the Regulations. It is a risk-based regulatory tool used to prioritise attention and resources towards areas of highest relative risk. The CRI is also shared with Ofwat as part of a coordinated regulatory approach. A CRI target of 2 is used as the threshold for financial penalties, providing a consistent performance benchmark.
The industry median CRI in 2025 was 2.92, an increase from 1.77 in 2024 and 2.32 in 2023. Interpretation of the industry median should take account of two factors: company performance and the effect of regulatory intervention, where notices served in response to risk can amplify the score. Dŵr Cymru Welsh Water recorded the highest company CRI score in 2025. This is of concern, although the amplification associated with transformation notices should also be considered.
Figure 6 shows the CRI scores, removing the multiplication factor caused by having live legal instruments applied to the asset which had the failed test. It also shows that the impact of the legal instruments has reduced in 2025 meaning fewer failed tests are at locations where improvements are already in-flight. This is a positive step change in the right direction, and should continue if the company maintains delivery of legal instrument milestones and outcomes.
Figure 6 – CRI over past 5 years – CRI scores in blue, CRI scores removing legal instrument multiplier in green
In 2025, the CRI for companies wholly or mainly operating in Wales was 6.73. This represents a deterioration from 4.08 in 2024, following an improvement from 7.257 in 2023. The overall CRI comprises scores from different parts of the water supply system, including treatment works, supply points, service reservoirs and zones.
At company level, Dŵr Cymru Welsh Water’s CRI improved from 7.736 in 2023 to 4.28 in 2024, before deteriorating to 7.1 in 2025. Hafren Dyfrdwy’s CRI increased from 0.112 in 2023 to 1.10 in 2024, and to 1.26 in 2025. Dŵr Cymru Welsh Water accounted for a significant proportion of the Wales CRI and exceeded the Wales overall CRI of 6.73. CRI enables the key contributors to each component of the score to be identified, helping to show where risks originate, as illustrated in Figure 7.
Figure 7 – Wales Compliance Risk Index for 2025
When comparing with the national picture, it can be seen that the greatest compliance risk is coliform detections in zones, with the secondary driver being iron failures in zones.
Figure 8 – Top 10 parameters by site
In Wales, breaches at large works supplying a high number of consumers continue to make a substantial contribution to the annual CRI score. In 2025, 39% of the total CRI score arose from three breaches, at Court Farm works, Llandinam works and Bretton works. This represents an increase on previous years, where high-scoring breaches occurred at Bretton works in 2024, Felindre works in 2023, Ponsticill works in 2022, and Felindre works and Court Farm works in 2021. Non-compliance at large works carries a higher relative risk because of the number of consumers supplied. Coliforms are indicator parameters and require precautionary action by companies to ensure the continuing protection of consumers.
In 2025, iron contributed 40% of the total CRI score in Wales, compared with 7% in 2024 and 33% in 2023. Although the proportion of the CRI score attributable to iron can vary depending on the scoring of other breaches, including those at large works, the number of iron breaches in Wales remains high: 17 in 2025, 13 in 2024, 14 in 2023 and 21 in 2022. Further detail on discolouration is included later in this report.
In total, there were 23 microbiological breaches at treatment works and service reservoirs in Wales in 2025, excluding E. coli detections. This was an increase from 14 breaches in 2024. Service reservoir breaches are considered in more detail later in this report.