Understand
London's super sewer significantly improves River Thames health, report reveals
Overview
According to a report by Thames Water, the health of the River Thames has improved significantly during the first year of operation for the new £5bn Thames Tideway Tunnel 'super sewer'. The 16-mile underground pipe network saw an 86% reduction in raw sewage entering the river in 2025 compared to previous averages, while preventing about 84 tonnes of litter from reaching the waterway. Although challenges from pollution and climate change remain, conditions for fish and aquatic wildlife have improved, and days with increased health risks linked to sewage overflows dropped from 269 in 2023 to 38 in 2025.
Key points
- A report by Thames Water shows an 86% reduction in raw sewage entering the River Thames in 2025.
- The £5bn Thames Tideway Tunnel prevented approximately 84 tonnes of litter, such as wet wipes, from reaching the waterway.
- Days of increased health risks linked to sewage overflows fell from 269 in 2023 to 38 in 2025.
- The 16-mile underground pipe network runs from Acton in the west to Abbey Mills in the east.
- Experts warn that ongoing pollution and climate change remain challenges, requiring continued action and investment.