Unmonitored Sewer Overflows: How We Exposed Thames Water’s Hidden Spillers

Hundreds of hidden sewer overflows have now been revealed on Thames Water’s map, thanks to relentless public pressure. This victory makes Thames Water more accountable, shifting the focus from shareholders to customers and the environment.

Our previous campaign to display real-time sewer spills online uncovered gaps in the official data. Evidence pointed to unmonitored outfalls not included in reports to the Environment Agency. After persistent information requests, Thames Water admitted to having over 100 unmonitored outfalls, most of them in London.

With the company planning to spend billions on infrastructure upgrades, this investment must be based on accurate data. Knowing there are double the number of overflows in London is critical. For example, the Brent Lodge Park sewer overflow featured in a Channel 4 Dispatches program, revealing spills that were not recorded in official reports (5m 48s).

Monitoring and Accountability: What’s Next?

We’ll be tracking these overflows closely to determine how often they discharge and pushing for stronger permits from the Environment Agency. However, past experience tempers our confidence. When asked about London’s most frequent spiller in Mayesbrook Park in Dagenham, East London, the Environment Agency admitted they had never inspected it or investigated its frequent discharges.

Protecting rivers requires a detailed, case-by-case approach. Sewer overflow by sewer overflow, we’ll root out weak permits and push for action. It’s granular, meticulous work—but essential. Special thanks to the Brent River and Canal Society for their help in monitoring the River Brent catchment.