Super sewer is cleaning up the Thames, says report

The health of the River Thames in London improved significantly in the first year of the new "super sewer", according to Thames Water.

A report by the company found an 86% reduction in raw sewage entering the river in 2025 compared with the previous average, while the sewer also prevented about 84 tonnes of litter, such as wet wipes and sanitary products, from reaching the waterway.

The sewer, called the Thames Tideway Tunnel, was built to increase capacity, allowing more rainwater and waste to be stored and reducing overflows into the tidal stretch of the Thames.

However, the report warned that pollution and climate change remained "big challenges" and said continued action was needed.

The 16-mile (26km) pipe flows deep underground from Acton in the west to Abbey Mills in the east.

At 23ft (7.2m) wide, it is big enough to store 600 Olympic-sized swimming pools of liquid, which is pumped to a vast sewage treatment works in Beckton, east London.

Thames Water - which has now taken over the running of the tunnel - said river users could now feel more confident about spending time on the water.

Its report - which assessed the environmental benefits from the tunnel - found that the number of days of increased health risks linked to sewage overflows had reduced from 269 in 2023 to 38 in 2025.

The firm said the stretch of river, once declared "biologically dead", was now "on the road to recovery".

The report also found that conditions for fish and other aquatic wildlife in the tidal Thames had improved since the super sewer began operating.

Tess Fayers, director of waste and bioresources at Thames Water, said: "This is an important milestone for the river and a significant step towards a cleaner, healthier and more resilient Thames for future generations."

The charity Thames21, which campaigns for healthier waterways, said the tunnel was "an impressive piece of engineering", however warned other methods of water management would be needed if extreme weather events caused by climate change became more frequent.

Its chief executive Chris Coode said: "We want to see more investment in nature-based solutions to tackle these problems, building wetlands that treat polluting outfalls, raingardens that manage surface water flooding...

"Trapping the water where it falls is always a much better way of doing it rather than trying to move it through a system for later treatment in sewage treatment works.

"How we manage the water we want to drink and disposing of our waste water at a time when we're going to have more extreme weather events... all of that is going to take a lot more than a great big tunnel."

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