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Polluted by sewage 184 times in 2025 - lasting 1,304 hours
Monitoring fell below 50% in some locations so could be more
Southampton Water was the #23 most polluted shellfish area in England & Wales, by duration of sewage overflows, as reported by the water companies
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Donate NowHere are all the reported sewage overflow totals for Southampton Water in 2025.
We use data from the water companies, but we are seeing many anomalies that make us believe that location information is quite poor. The situation is likely far worse than reported here.
In particular: Totals on this page can differ from totals in the Ranked Shellfish page - number on this page are higher - this is due to a lack of standardization on shellfish area names. This page more accurately counts the differing names. For example "Solway" and "SOLWAY" are counted as different in the rankings, but correctly aggregated here.
Other CSO Combined Sewage Overflow - a device that, when operating, pours combined rainwater & sewage into a waterway s may also be located nearby, however the water companies claim that these do not affect the water quality here.
| Company | Waterway | Site | Sewage Dumps | Duration (Hours) | Reporting % |
|---|---|---|---|---|---|
| Southern Water | River Test | MILLBROOK WWTW | 28 | 439 | 99.9 |
| Southern Water | River Itchen Estuary | PORTSWOOD WWTW | 36 | 380 | 99.9 |
| Southern Water | Southampton Water | SLOWHILL COPSE WWTW | 22 | 229 | 99.9 |
| Southern Water | River Itchen Estuary | WOOLSTON WWTW | 18 | 78 | 99.1 |
| Southern Water | Bartley Water | DOWNS PARK TOTTON CEO | 12 | 69 | 98.3 |
| Southern Water | Itchen Estuary | LAWN ROAD/OSBOURNE ROAD | 11 | 48 | 46.5 |
| Southern Water | River Itchen | IMPERIAL ROAD MOUNT PLEASANT CEO | 7 | 15 | 99.9 |
| Southern Water | River Itchen Estuary | CHAPEL WHARF WPS | 3 | 9 | 26.4 |
| Southern Water | River Test | MILLBROOK WWTW | 6 | 9 | 99.9 |
| Southern Water | River Test | BLECHYNDEN TERRACE SOUTHAMPTON CSO | 6 | 8 | 100 |
| Southern Water | River Itchen | SIRDAR ROAD SOUTHAMPTON CSO | 17 | 6 | 100 |
| Southern Water | Test Estuary | CAWTE ROAD/PARK ROAD CSO | 10 | 4 | 100 |
| Southern Water | River Itchen | GATERS MILL | 2 | 4 | 100 |
| Southern Water | Itchen Estuary | SOUTHCLIFF ROAD/LIVERPOOL STREET | 3 | 0 | 99.7 |
| Southern Water | River Itchen | UPR SHAFTESBURY AVE SOUTHAMPTON CSO | 1 | 0 | 99.9 |
| Southern Water | Saline Estuary | WESSEX LANE SOUTHAMPTON OUTSIDE 11 | 2 | 0 | 95 |
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