# Sewage spills in England

Every monitored storm overflow in England, from the Environment Agency's annual returns. This is the national record: how often raw sewage was released, by which company, into which rivers, and whether it is getting better or worse. There were 291,492 spills in 2025 across 14,272 monitored overflows. That was about a third lower than 2024, but 2025 was a dry year, and in the wet years either side overflows spilled more than 450,000 times.

Source page: https://britishresilienceindex.com/deep-dive/sewage
Machine readable data: https://britishresilienceindex.com/data/deep-dive/sewage.json

## How to read this

These are the water companies' own figures, reported to the Environment Agency under the Event Duration Monitoring scheme and published as open data. The headline measure is the number of spills, counted by the 12 to 24 hour method. Volume is not measured, only how often and for how long each overflow discharged. Storm overflow activity tracks rainfall, so a wetter year produces more spills: the level matters more than any single year on year change.

## Spills by water company, 2025

Every company's monitored overflows in 2025, ranked by the number of spills, with the total hours they discharged and how many overflow sites each one runs. These are the companies' own returns.

| company | spills | hours | sites |
|---|---|---|---|
| United Utilities | 60,843 | 327,453 | 2,270 |
| Yorkshire Water | 51,431 | 285,931 | 2,184 |
| South West Water | 46,164 | 407,006 | 1,358 |
| Severn Trent Water | 36,471 | 200,361 | 2,432 |
| Northumbrian Water | 27,776 | 123,521 | 1,561 |
| Wessex Water | 24,442 | 190,666 | 1,346 |
| Anglian Water | 16,779 | 101,598 | 1,442 |
| Southern Water | 15,554 | 114,868 | 977 |
| Thames Water | 9,189 | 107,822 | 580 |
| Welsh Water (England) | 2,843 | 14,525 | 122 |

## Spills by year, 2020 to 2025

Total spills recorded each year. The swing is large because it follows the weather: 2022 and 2025 were dry, 2023 and 2024 were wet. Monitoring also grew over this period, reaching near complete coverage by 2023, so the earliest years slightly understate the true total.

**Series**

| year | spills |
|---|---|
| 2,020 | 403,171 |
| 2,021 | 372,533 |
| 2,022 | 301,091 |
| 2,023 | 464,056 |
| 2,024 | 450,398 |
| 2,025 | 291,492 |

- **Note**: Spills track rainfall, not just performance. The duration tells the structural story: overflows discharged for 3.6 million hours in 2023 and 3.6 million in 2024, and still 1.9 million in the dry 2025. Source: Environment Agency EDM annual returns 2020 to 2025.

## The rivers and waters hit hardest, 2025

The named receiving waters that took the most spills in 2025, with the number of overflow outfalls discharging into each. Unnamed tributaries are excluded.

| name | spills | outfalls |
|---|---|---|
| River Derwent | 3,523 | 108 |
| River Calder | 3,208 | 91 |
| River Aire | 2,746 | 96 |
| North Sea | 2,491 | 120 |
| River Tame | 2,149 | 102 |
| River Avon | 2,053 | 117 |
| River Irwell | 1,837 | 68 |
| River Don | 1,700 | 68 |
| River Wharfe | 1,476 | 39 |
| River Ouse | 1,458 | 42 |
| River Trent | 1,434 | 83 |
| River Severn | 1,379 | 68 |

## The overflows that spilled most often, 2025

A storm overflow is meant to operate only in heavy rain, as a relief valve to stop sewage backing up into homes. These individual overflows spilled most often in 2025, in all weathers.

| site | company | water | spills |
|---|---|---|---|
| Croyde STW SO Croyde | South West Water | Croyde Bay (coastal) | 253 |
| Melton STW | Yorkshire Water | River Humber | 245 |
| Shop STW SO Shop | South West Water | Unnamed watercourse | 243 |
| Salcombe Regis STW SO Salcombe Regis | South West Water | Salcombe Regis Stream | 235 |
| Horns Cross STW SO Horns Cross | South West Water | Unnamed watercourse | 230 |
| Lock Lane CSO | United Utilities | Manchester Ship Canal | 217 |
| Town Quay Spst PSCSOEO Fowey | South West Water | River Fowey Estuary (e) | 198 |
| Abbotsham STW SO Abbotsham | South West Water | Kenwith Stream | 196 |
| Tatworth STW SSO Tatworth | South West Water | Forton Brook | 189 |
| Lydney STW (ssto) | Severn Trent Water | River Severn Estuary | 178 |
| Rewe STW SSO Rewe | South West Water | River Culm | 175 |
| High Bickington STW SO High Bickington | South West Water | Unnamed watercourse | 173 |
| Blennerhassett Ww PS | United Utilities | River Ellen | 172 |
| Brayford STW SO Brayford | South West Water | River Bray(s) | 172 |
| Marske STW | Yorkshire Water | Marske Beck | 170 |

## Five things the data makes clear

- Some overflows spill almost permanently. In 2024 one South West Water overflow at Salcombe Regis in Devon discharged for 8,773 hours, which is 365 days, essentially the entire year. A storm overflow is designed to operate only in exceptional rain.
- This is not only a rivers problem. In 2025, 1,165 monitored overflows discharged at or near designated bathing waters, the beaches and lakes where people swim, spilling 24,513 times between them.
- Monitoring is recent. The number of monitored overflows rose from 862 in 2016 to 12,092 in 2020 and 14,254 by 2024, when the Environment Agency reported near complete coverage. The earliest annual totals here therefore understate the true picture.
- A fall between two years is not progress in itself. Spill counts move with rainfall, so a dry year like 2025 produces fewer spills without a single pipe being fixed. The structural level, hundreds of thousands of spills even in a dry year, is what matters.
- A spill count measures events, not volume. The water released is not metered, so a long discharge and a brief one count the same. Duration is the better guide to how long a river was exposed.

## Sources

- Environment Agency, Event Duration Monitoring storm overflow annual returns 2020 to 2025 (https://www.data.gov.uk/dataset/19f6064d-7356-466f-844e-d20ea10ae9fd/event-duration-monitoring-storm-overflows-annual-returns) · Open Government Licence v3.0

## Caveats and data notes

- These are the water companies' own EDM returns, published by the Environment Agency under the Open Government Licence.
- The headline is the number of spills, counted by the 12 to 24 hour method. Volume of sewage is not measured.
- Year to year totals track rainfall. A wetter year produces more spills, so a change between two years is not on its own a measure of performance.
- Monitoring coverage grew over the period, reaching near complete by 2023, so the earliest years slightly understate the true national total.
- The returns cover storm overflows in England. Welsh Water appears only for its overflows located in England; overflows in Wales are published separately by Natural Resources Wales.
- Contains public sector information licensed under the Open Government Licence v3.0.

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British Resilience Index, a non-partisan UK civic data project. Every figure is
reconciled to its primary official publisher before it is shown. Free to cite with
attribution: https://britishresilienceindex.com