Polluted by sewage 2,976 hours in 2025 , monitoring offline 1,256 hours
What's a potential overflow? If the CSO goes 'Offline' while its Overflowing, we don't know if it stopped overflowing until we get a 'Stop' event.
Your local MP is Chris Hinchliff (Labour) - Find out more about their interests, donors, and voting at They Work For You
Please consider a one-off or small recurring donation. We need your help to keep this site going.
Donate Now| Company | Site Name | Receiving Waterway | Overflow Days | Total Duration (hours) | Offline/Potential Pollution |
|---|---|---|---|---|---|
| Anglian Water | SHENFIELD SEWER SSO | River Wid | 54 | 646h 12m | - |
| Thames Water | Cottered STW | Cottered Brook | 32 | 539h 15m | - |
| Anglian Water | BARLEY STW | Fowlmere Stream | 40 | 530h 45m | - |
| Anglian Water | LETCHWORTH-NORTON COMMON SSO | Pix Brook | 28 | 512h 17m | - |
| Thames Water | Weston STW | Weston | 30 | 370h 30m | - |
| Thames Water | Barkway STW | River Quin | 7 | 93h | - |
| Thames Water | Weston STW | Weston | 8 | 90h 45m | - |
| Thames Water | Therfield STW | River Rib | 12 | 68h 15m | 721 h |
| Thames Water | Cottered STW | Cottered Brook | 6 | 54h 15m | - |
| Anglian Water | BALDOCK-NORTON ROAD SP | Onto Land | 5 | 28h 12m | - |
| Thames Water | Standon STW | Rib | 3 | 12h 30m | - |
| Thames Water | Chapmore End STW | Rib | 7 | 9h 45m | - |
| Thames Water | Buntingford STW | River Rib | 3 | 5h 15m | - |
| Anglian Water | BARLEY STW | Fowlmere Stream | 5 | 5h 12m | 270 h |
| Anglian Water | LETCHWORTH-NORTON COMMON SSO | Pix Brook | 1 | 5h 7m | - |
| Anglian Water | ASHWELL STW | River Rhee | 8 | 4h 51m | - |
| Thames Water | Chapmore End STW | Rib | 0 | 0h | - |
| Anglian Water | SANDON (NEW) STW | Cat Of River Ivel | 0 | 0h | - |
| Thames Water | Barkway STW | River Quin | 0 | 0h | - |
| Thames Water | Buntingford STW | River Rib | 0 | 0h | - |
| Anglian Water | Letchworth WRC | Pix Brook, River Gt Ouse | 0 | 0h | 0 h |
| Thames Water | Therfield STW | River Rib | 0 | 0h | 264 h |
| Anglian Water | BALDOCK-NORTON ROAD SP | Onto Land | 0 | 0h | - |
| Thames Water | Standon STW | Rib | 0 | 0h | - |
| Anglian Water | ASHWELL STW | River Rhee | 0 | 0h | - |
EDM (Event Duration Monitoring) data and Consented Discharges to Controlled Waters with Conditions from Environment Agency & Data Map Wales, and Scottish Water
Experimental derived data from Thames Water API, Some data may be missing or inaccurate. Live sewage data from Stream Water API
Annual figures up to and including 2025 come from official water company returns. The 2026 figure is our own estimate, derived continuously from the companies' live data feeds.
Uses Environment Agency rainfall data from the real-time data API (Beta) - Rainfall data is delayed by up to two days.
This website is intended to provide an accurate representation of the Environment Agency data. The data is hard to use, and thus some errors may have been made. If you find something that is incorrect, please raise an issue at the GitHub issues page and we'll endeavour to fix it quickly.
This project is not associated, approved or endorsed by any of the companies whose logos you see here.