- Drinking Water 2025 – Summary of the Chief Inspector’s report for drinking water in England
- Foreword
- Water supplies and testing
- Compliance with water quality standards
- Learning from microbiological failures
- Learning from turbidity failures
- Learning from chemical, taste and odour failures
- Learning from pesticide failures
- Asset health and service reservoir integrity
- Consumer contacts
- Drinking water quality events
- Water safety planning and risk assessment
- Perfluoroalkyl and polyfluoroalkyl substances (PFAS)
- Audit programme completed by the Inspectorate
- Air valve audits
- Enforcement, transformation and recommendations
- Materials in contact with drinking water (regulation 31)
- Security and Emergency Measures Direction - SEMD
- Network and Information Systems - NIS
- Research publications
- 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) (referred to as the Regulations) 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 2025.
Compliance with the drinking water standards is consistently high in England. However, scrutinising company water safety plans, audits and events can 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.
Compliance Risk Index (CRI) illustrates the impact of a compliance failure on company performance, and the potential impact 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 2025, 447 were related to consumer distribution systems.
Sampling shortfalls
The number of samples required to be taken is specified in the Regulations. In 2025 companies reported the following sampling shortfalls in Table 5.
| Company code | Number of tests per company | Target number of tests | Number of sample shortfalls | Shortfall |
|---|---|---|---|---|
| AWI | 1698 | 1,730 | 32 | 1.85% |
| AFW | 189,963 | 190,139 | 176 | 0.09% |
| ALB | 963 | 963 | 0 | 0% |
| ANH | 384,310 | 384,591 | 281 | 0.07% |
| BRL | 90,027 | 90,127 | 100 | 0.11% |
| CAM | 29,664 | 30,193 | 529 | 1.75% |
| ESP | 10,661 | 10,661 | 0 | 0% |
| IWN | 38,221 | 41,189 | 2968 | 7.21% |
| LMW | 17,537 | 17,867 | 330 | 1.85% |
| LNW | 19,509 | 19,511 | 2 | 0.01% |
| NES | 265,978 | 266,146 | 168 | 0.06% |
| PRT | 48,870 | 49,440 | 570 | 1.15% |
| SES | 12,582 | 12,730 | 148 | 1.16% |
| SEW | 208,580 | 209,223 | 643 | 0.31% |
| SRN | 225,207 | 225,305 | 98 | 0.04% |
| SST | 65,670 | 65,680 | 10 | 0.02% |
| SVT | 452,105 | 452,290 | 185 | 0.04% |
| SWB | 214,966 | 215,456 | 490 | 0.23% |
| TMS | 436,206 | 436,304 | 98 | 0.02% |
| UUT | 385,624 | 386,805 | 1,181 | 0.31% |
| VWP | 2,660 | 2,660 | 0 | 0% |
| WSX | 179,001 | 179,632 | 631 | 0.35% |
| YKS | 388,919 | 389,491 | 572 | 0.15% |
| Total | 3,698,820 | 3,666,843 | 6,244 | 0.17% |
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 Risk Index by company
The Compliance Risk Index (CRI) is not a statutory measure and does not remove a company’s obligation to comply with each parametric value set out in the Regulations. However, as a risk-based metric, its purpose is to incentivise companies to focus their resources on 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 framework, designed to drive improvements in water quality in the public interest. While the Inspectorate does not consider any compliance failures to be acceptable, a CRI target of 2 has been established as the threshold above which financial penalties may apply. This ensures that outcomes remain risk-focused, proportionate, and achievable.
Looking ahead, the CRI target will become more stringent, reducing to 1.5 at the start of AMP8 and further to 1.0 by the end of the AMP8 period.
The median CRI value for the industry in 2025 is 2.905 (2.687 England), representing a shift in risk focus driven by regulatory activity when compared with 1.741 in 2024, 3.040 in 2023, 1.365 in 2022, and 1.171 in 2021.
Interpreting the median CRI across the industry is complex, as it reflects both company performance and regulatory intervention. In particular, the use of enforcement actions, such as notices issued in response to identified risks, is intended to increase the CRI score where appropriate, thereby directing attention towards areas of greatest concern. As a result, companies in the upper half of the distribution typically reflect the presence of ongoing strategic risks and associated regulatory action.
The overall CRI is derived from performance across distinct components of the water supply chain, including treatment works, supply points, service reservoirs, and water supply zones. It incorporates all regulatory failures, including indicator parameters measured at treatment works, service reservoirs, and consumer taps. This comprehensive approach ensures that all risks and locations requiring improvement are captured within the metric.
Failures at water treatment works make the largest contribution to company CRI scores. This is due to the large populations served by these assets, meaning that any failure represents a higher risk to public health. As these sites are fully within company control, such failures are expected to be effectively mitigated and, where possible, avoided.
Figure 3 – 5 year CRI
Figure 4 – 5 year CRI
Figure 5 – Company CRI 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 6.
Figure 6 – 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