England's water companies ranked by pollution record, worst first
The nine water and sewerage companies in England, ranked from the worst to the best environmental record over the four years 2021 to 2024, with the serious pollution incidents and sewage spills behind it.
England's nine water and sewerage companies are rated every year on how well they protect rivers, seas and land: how many pollution incidents they cause, whether they keep to their permits, and how often they report their own problems. Each company earns one to four stars a year, and four is the best.
The table adds up each company's stars for 2021 to 2024 (the most possible is 16) and puts the lowest totals first, so the worst record is at the top. Thames Water, Southern Water and South West Water tie on 7 stars, and Thames Water had the lowest rating in 2024, at one star. The figures on serious incidents and sewage spills are below the table.
Key figures
Water companies in England by cumulative star rating, 2021 to 2024
Rank 1 is the worst record: the fewest stars over four years. Companies on the same total share a rank. Ratings for 2025 had not been published.
| Rank | Water company | Stars, 2021 to 2024 (most possible: 16) | Years |
|---|---|---|---|
| 1= | Thames Water | 7 | 2021 to 2024 |
| 1= | Southern Water | 7 | 2021 to 2024 |
| 1= | South West Water | 7 | 2021 to 2024 |
| 4 | Anglian Water | 8 | 2021 to 2024 |
| 5 | Yorkshire Water | 9 | 2021 to 2024 |
| 6 | Wessex Water | 10 | 2021 to 2024 |
| 7 | Northumbrian Water | 12 | 2021 to 2024 |
| 8 | United Utilities | 13 | 2021 to 2024 |
| 9 | Severn Trent Water | 16 | 2021 to 2024 |
Serious pollution incidents, 2024
- There were 75 serious pollution incidents in 2024, up 60% from 47 in 2023.
- Thames Water had 33 of them, Southern Water 15 and Yorkshire Water 13: 61 of the 75 came from those three companies.
- Total pollution incidents, from category 1 to 3, rose to 2,801 in 2024, the highest number since 2011.
| Category | Stars (most possible: 16) |
|---|---|
| Thames Water | 7 |
| Southern Water | 7 |
| South West Water | 7 |
| Anglian Water | 8 |
| Yorkshire Water | 9 |
| Wessex Water | 10 |
| Northumbrian Water | 12 |
| United Utilities | 13 |
| Severn Trent Water | 16 |
Sewage spills from storm overflows, 2024
- Storm overflows spilled 450,398 times in 2024, for 3,614,428 hours of monitored spills, an average of 31.8 spills per overflow.
- 12.5% of storm overflows did not record a spill, and 39.0% operated 10 times or fewer.
Star ratings, 2024
- The nine companies earned 19 stars in 2024, the lowest total since the ratings began in 2011, and only Severn Trent Water reached four stars.
- Thames Water earned 2 stars in each of 2021, 2022 and 2023, then 1 star in 2024.
What the numbers mean
Stars are a regulator's summary of many measures, so one bad year can pull a company down. Thames Water earned 2 stars in each of 2021, 2022 and 2023, then 1 star in 2024. Severn Trent Water is the only company to have earned 4 stars in each of the last six years.
The incident counts are raw numbers, not rates: a company with more sewers has more places for something to go wrong. Across all nine companies, the 2,801 pollution incidents of 2024 were the most since 2011, and 61 of the 75 serious ones came from three companies. The storm overflow total counts every spill from every monitored overflow, so it says as much about the size of a network as about how well it is run.