Polluted by sewage 6,556 hours in 2025 , monitoring offline 5,731 hours , potential overflows 651 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.
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Donate Now| Company | Site Name | Receiving Waterway | Overflow Days | Total Duration (hours) | Offline/Potential Pollution |
|---|---|---|---|---|---|
| Thames Water | Church Hanborough STW | Hanborough Stream | 70 | 1,033h 15m | - |
| Thames Water | Church Hanborough STW | Hanborough Stream | 38 | 684h 45m | - |
| Thames Water | South Leigh STW | Limb Brook | 26 | 550h 15m | - |
| Thames Water | Weston-on-the-Green STW | Gallos Brook | 21 | 415h 30m | - |
| Thames Water | Charlton-on-Otmoor STW | Oxon Ray | 28 | 414h | - |
| Thames Water | Charlton-on-Otmoor STW | Oxon Ray | 26 | 398h | - |
| Thames Water | South Leigh STW | Limb Brook | 22 | 377h | - |
| Thames Water | Horton-Cum-Studley STW | Danes Brook | 40 | 299h 45m | 928 h |
| Thames Water | Combe STW | Evenlode | 18 | 298h | - |
| Thames Water | Islip STW | River Ray | 14 | 285h 45m | - |
| Thames Water | Weston-on-the-Green STW | Gallos Brook | 20 | 280h 30m | - |
| Thames Water | Bletchingdon STW | Bletchingdon Brook | 29 | 258h | 219 h |
| Thames Water | Bicester STW | Langford Brook | 17 | 231h 15m | - |
| Thames Water | Bicester STW | Langford Brook | 17 | 217h 30m | - |
| Thames Water | Upper Heyford STW | Cherwell | 15 | 160h 45m | - |
| Thames Water | Upper Heyford STW | Cherwell | 14 | 136h 15m | - |
| Thames Water | Middleton Stoney STW | Gagle Brook | 12 | 96h 45m | - |
| Thames Water | Combe STW | Evenlode | 8 | 63h 30m | - |
| Thames Water | Woodstock STW | River Glyme | 8 | 60h | 667 h |
| Thames Water | Middleton Stoney STW | Gagle Brook | 7 | 50h | 0 h |
| Thames Water | Tackley SPS & Storm SPS | Rver Cherwell | 4 | 47h 15m | - |
| Anglian Water | ARDLEY STW | Stoke Lyne Brook | 7 | 45h 16m | - |
| Thames Water | Bletchingdon STW | Bletchingdon Brook | 4 | 38h 15m | - |
| Anglian Water | WESTBURY STW | River Great Ouse | 11 | 29h 51m | 0 h |
| Thames Water | Islip STW | River Ray | 2 | 29h 15m | 3,331 h |
| Thames Water | Woodstock STW | River Glyme | 12 | 28h 45m | - |
| Thames Water | Weston-on-the-Green SPS | Gallos Brook | 2 | 21h 14m | - |
| Anglian Water | ARDLEY STW | Stoke Lyne Brook | 1 | 3h 59m | - |
| Anglian Water | WESTBURY STW | River Great Ouse | 3 | 1h 13m | - |
| Thames Water | Horton-Cum-Studley STW | Danes Brook | 1 | 0h 30m | 651 h |
| Thames Water | XX (Bucknell) SPS | Town Brook | 0 | 0h | 584 h |
| Thames Water | XX (Bucknell) SPS | Town Brook | 0 | 0h | - |
| Thames Water | Weston-on-the-Green SPS | Gallos Brook | 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.