Polluted by sewage 1,927 hours in 2026 so far..
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 |
|---|---|---|---|---|---|
| Dwr Cymru Welsh Water | Ball Lane Storm Overflow | River Rhymni | 73 | 1,428h 23m | - |
| Dwr Cymru Welsh Water | Cardiff Kimberley Road Storm Overflow | River Rhymni | 31 | 494h 44m | - |
| Dwr Cymru Welsh Water | Fishpond Road Storm Overflow | River Rhymni | 3 | 3h 57m | - |
| Dwr Cymru Welsh Water | Dowlands Way Cardiff Storm Overflow | River Rhymni | 0 | 0h | - |
| Dwr Cymru Welsh Water | Cardiff Pen-y-lan Road Storm Overflow | Roath 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.