Polluted by sewage 127 hours in 2025 , monitoring offline 891 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 | Mays Lane Overflow | N/A | 23 | 70h 8m | - |
| Thames Water | Mays Lane Overflow | N/A | 8 | 28h 40m | - |
| Thames Water | Lytton road sso | Pymmes Brook | 3 | 12h | - |
| Thames Water | Western way | Dollis Brook | 2 | 8h 30m | - |
| Thames Water | Lytton road sso | Pymmes Brook | 1 | 3h 15m | - |
| Thames Water | Western way | Dollis Brook | 1 | 2h 30m | - |
| Thames Water | Oak Hill Park CSO | N/A | 2 | 1h 20m | - |
| Thames Water | Church hill road, barnet | Pymmes Brook | 1 | 0h 45m | - |
| Thames Water | Puller rd/calvert rd storm, barnet | Kitts End Stream | 0 | 0h | - |
| Thames Water | Puller rd/calvert rd storm, barnet | Kitts End Stream | 0 | 0h | 603 h |
| Thames Water | Netherlands Road CSO | N/A | 0 | 0h | - |
| Thames Water | Oak Hill Park CSO | N/A | 0 | 0h | 288 h |
| Thames Water | Church hill road, barnet | Pymmes 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.