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Polluted by sewage 4,054 hours in 2025 , monitoring offline 2,480 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 | Little Milton STW | Gainsbridge Brook | 54 | 1,165h 15m | - |
| Thames Water | Wheatley STW | Wheatley Ditch | 53 | 784h 45m | 213 h |
| Thames Water | Benson STW | Howbery Ditch | 18 | 361h 2m | 398 h |
| Thames Water | Wheatley STW | Wheatley Ditch | 28 | 326h | - |
| Thames Water | Thame STW | Lashlake Stream | 22 | 325h 30m | - |
| Thames Water | Chalgrove STW | Warpsgrave Ditch | 15 | 239h 15m | - |
| Thames Water | Little Milton STW | Gainsbridge Brook | 11 | 146h 45m | - |
| Thames Water | Chinnor STW | Henton Stream | 30 | 142h | 621 h |
| Thames Water | Thame STW | Lashlake Stream | 10 | 135h 30m | - |
| Thames Water | Watlington STW | Pyrton Stream | 28 | 128h 15m | - |
| Thames Water | Dorchester STW | Thame | 12 | 116h 59m | - |
| Thames Water | Friday Street (Henley) SPS | Thames | 6 | 44h 44m | 527 h |
| Thames Water | Chalgrove STW | Warpsgrave Ditch | 6 | 39h 30m | - |
| Thames Water | Tetsworth STW | Latchford Brook | 5 | 34h 30m | - |
| Thames Water | Chinnor STW | Henton Stream | 6 | 26h 10m | - |
| Thames Water | Beckley STW | Otmoor Lane Ditch | 3 | 19h | - |
| Thames Water | Tetsworth STW | Latchford Brook | 2 | 8h 15m | - |
| Thames Water | Beckley STW | Otmoor Lane Ditch | 1 | 5h | - |
| Thames Water | Forest Hill STW | Polecat End Ditch | 2 | 3h 30m | - |
| Thames Water | Sonning Common STW | Into Land | 1 | 1h 30m | - |
| Thames Water | Friday Street (Henley) SPS | Thames | 1 | 0h 56m | 171 h |
| Thames Water | Manor Farm Road (Sydenham) SPS | Sydenham Stream | 0 | 0h | - |
| Thames Water | Caversham (Reading) SPS | Thames | 0 | 0h | - |
| Thames Water | Watlington STW | Pyrton Stream | 0 | 0h | - |
| Thames Water | Dorchester STW | Thame | 0 | 0h | - |
| Thames Water | Forest Hill STW | Polecat End Ditch | 0 | 0h | - |
| Thames Water | Benson STW | Howbery Ditch | 0 | 0h | - |
| Thames Water | Caversham (Reading) SPS | Thames | 0 | 0h | 548 h |
| Thames Water | Sonning Common STW | Into Land | 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.
Get in touch if you have queries or want to discuss our data.
press [at] top-of-the-poops.org