England's drinking water companies ranked by compliance risk
The 21 water suppliers in England ranked by the Drinking Water Inspectorate's compliance risk score for 2025, the highest risk first.
Every water company has to test its drinking water and report any test that fails a legal standard. The compliance risk score turns those failures into one number for each company: it weighs how serious each failure was and how many people it could affect, so a failure at a works that serves many people counts for more.
The table ranks the 21 suppliers in England by their 2025 score, with the highest risk first: Thames Water Utilities 4.32, Bristol Water 3.95 and Northumbrian, Essex and Suffolk Water 3.90, down to SES Water at 0.00. The middle score for England was 2.687, and a score of 2 is the level above which financial penalties may apply.
Key figures
Compliance risk score by company, England, 2025
Rank 1 has the highest risk. The score is the total of four parts, treatment works, service reservoirs, supply points and consumer-tap zones, added up from the report's chart data. Two small suppliers whose names are not given in the report are left out. Company names are as the report's glossary gives them.
| Rank | Water supplier | Compliance risk score for 2025 (higher means more serious test failures; 2 is the level above which penalties may apply) | Year |
|---|---|---|---|
| 1 | Thames Water Utilities | 4.32 | 2025 |
| 2 | Bristol Water | 3.95 | 2025 |
| 3 | Northumbrian, Essex and Suffolk Water | 3.90 | 2025 |
| 4 | Independent Water Networks | 3.63 | 2025 |
| 5 | Southern Water | 3.19 | 2025 |
| 6 | Affinity Water | 3.17 | 2025 |
| 7 | Yorkshire Water | 3.15 | 2025 |
| 8 | Anglian Water | 3.13 | 2025 |
| 9 | United Utilities Water | 2.11 | 2025 |
| 10 | South East Water | 2.08 | 2025 |
| 11 | South West and Bournemouth Water | 1.37 | 2025 |
| 12 | South Staffordshire Water | 1.26 | 2025 |
| 13 | Severn Trent Water | 1.24 | 2025 |
| 14 | Wessex Water | 0.92 | 2025 |
| 15 | ESP Water | 0.77 | 2025 |
| 16 | Cambridge Water Company | 0.53 | 2025 |
| 17 | Portsmouth Water | 0.45 | 2025 |
| 18 | Icosa Water | 0.30 | 2025 |
| 19 | Leep Networks Water | 0.03 | 2025 |
| 20= | Veolia Water Projects | 0.00 | 2025 |
| 20= | SES Water | 0.00 | 2025 |
How to read the score
- The median compliance risk score was 2.905 for the whole industry and 2.687 for England in 2025, against 1.741 in 2024, 3.040 in 2023, 1.365 in 2022 and 1.171 in 2021.
- A score of 2 is the threshold above which financial penalties may apply, and the target will tighten to 1.5 at the start of the next regulatory period and to 1.0 by the end of it.
- Failures at water treatment works make the largest contribution to company scores, because the large populations they serve make any failure a higher risk to public health.
- Of all the compliance failures during 2025, 447 were related to consumer distribution systems.
The 10 water suppliers in England with the worst drinking water risk scores, 2025
| Category | Compliance risk score (2 is the level above which penalties may apply) |
|---|---|
| Thames Water Utilities | 4.32 |
| Bristol Water | 3.95 |
| Northumbrian, Essex and Suffolk Water | 3.9 |
| Independent Water Networks | 3.63 |
| Southern Water | 3.19 |
| Affinity Water | 3.17 |
| Yorkshire Water | 3.15 |
| Anglian Water | 3.13 |
| United Utilities Water | 2.11 |
| South East Water | 2.08 |
What the numbers mean
The score is a guide to where risk sits, not a grade for the water in your tap. It is not a legal pass mark: a company must meet every standard whatever its score. It also reflects the regulator's own actions, because issuing a notice is meant to raise a company's score, which is why the middle score is higher in 2025 than in 2024.
A high score can come from one part of a company. Failures at treatment works count the most because they can affect many people, so look at the parts of a company's score, treatment works, reservoirs, supply points and taps, before drawing a conclusion about the water it supplies. A score of 0.00 means no scored failures in 2025.
Sources
- Compliance with water quality standards - Drinking Water Inspectorate
- Drinking Water 2025 - Summary of the Chief Inspector’s report for drinking water in England - Drinking Water Inspectorate
- Drinking Water 2025: Figure 5, company compliance risk index scores, England (Drinking Water Inspectorate chart data)