Water companies in England ranked by pollution incidents
The nine water and sewerage companies in England ranked by the pollution incidents they caused in 2024, the most first, with each company's best and worst year since 2016.
A pollution incident is an event in which a water company's sewers, pipes or treatment works harm rivers, land or the sea. The regulator counts them in three categories, from the most serious (category 1) to the least (category 3), and this page counts categories 1 to 3 together. Each count is for one company in one year.
The table ranks the nine companies by their 2024 total, and the sector total was 2,801, up from 2,174 in 2023. Thames Water had the most, 523, then Anglian Water with 482; Northumbrian Water had the fewest, 134. Below the table, each company's best and worst year from 2016 to 2024 is listed, with the three-year average that smooths out one-off bad years.
Key figures
Pollution incidents in 2024, by company
Rank 1 caused the most pollution incidents in 2024. The counts cover incidents from sewerage and water supply assets, categories 1 to 3. The figures for 2025 are due in 2026.
| Rank | Water company | Pollution incidents in 2024 (times a company's sewers, pipes or works harmed rivers, land or sea) | Year |
|---|---|---|---|
| 1 | Thames Water | 523 | 2024 |
| 2 | Anglian Water | 482 | 2024 |
| 3 | United Utilities | 376 | 2024 |
| 4 | Southern Water | 332 | 2024 |
| 5 | Severn Trent Water | 300 | 2024 |
| 6 | Wessex Water | 248 | 2024 |
| 7 | South West Water | 209 | 2024 |
| 8 | Yorkshire Water | 197 | 2024 |
| 9 | Northumbrian Water | 134 | 2024 |
The sector in 2024
- The nine companies caused 2,801 pollution incidents in 2024, a rise of 29% from 2,174 in 2023.
- Eight of the nine companies had more incidents in 2024 than in 2023; only South West Water had fewer.
Each company's best and worst year, 2016 to 2024
- Thames Water: its best year was 2021, with 304 incidents, and its worst was 2024, with 523; its three-year average in 2023 was 437.7.
- Anglian Water: its best year was 2018, with 216 incidents, and its worst was 2024, with 482; its three-year average in 2023 was 377.3.
- United Utilities: its best year was 2020, with 145 incidents, and its worst was 2024, with 376; its three-year average in 2023 was 258.7.
- Southern Water: its best year was 2017, with 135 incidents, and its worst was 2019, with 458; its three-year average in 2023 was 325.3.
- Severn Trent Water: its best year was 2020, with 232 incidents, and its worst was 2018, with 330; its three-year average in 2023 was 279.0.
- Wessex Water: its best year was 2016, with 96 incidents, and its worst was 2024, with 248; its three-year average in 2023 was 185.3.
- South West Water: its best year was 2022, with 136 incidents, and its worst was 2020, with 235; its three-year average in 2023 was 189.3.
- Yorkshire Water: its best year was 2022, with 145 incidents, and its worst was 2016, with 262; its three-year average in 2023 was 172.0.
- Northumbrian Water: its best year was 2017, with 59 incidents, and its worst was 2024, with 134; its three-year average in 2023 was 109.0.
| Category | Pollution incidents in 2024 |
|---|---|
| Thames Water | 523 |
| Anglian Water | 482 |
| United Utilities | 376 |
| Southern Water | 332 |
| Severn Trent Water | 300 |
| Wessex Water | 248 |
| South West Water | 209 |
| Yorkshire Water | 197 |
| Northumbrian Water | 134 |
What the numbers mean
These are counts of events, not rates, so a company with a bigger network has more places for something to go wrong. Thames Water's 523 incidents and Northumbrian Water's 134 are not directly comparable without the size of each network, but the trend within one company is: Anglian Water had 236 incidents in 2016 and 482 in 2024.
Eight of the nine companies caused more incidents in 2024 than in 2023, and only South West Water caused fewer. Because a single bad year can distort a ranking, the page also shows each company's best and worst year and its three-year average.