Data released today shows storm overflow performance in 2025 was the best ever, with the total number of spills from Anglian Water’s storm overflows reduced by more than 60% and the total duration of all spills reduced by more than 80%% compared to 2024.

New storm tank at Ramsey Water Recycling Centre

The East of England is set to benefit from more than £269 million of investment to reduce spills from storm overflows this year as Anglian Water continues its largest ever investment plan for the region.

The AMP8 investment planned for this year is part of a £1 billion package being delivered by 2030 to tackle storm overflows and includes installing nature-based solutions, such as wetlands and sustainable drainage, alongside traditional infrastructure, including storage tanks to reduce the pressure on sewers, as well as improved monitoring to predict and prevent spills.

Storm overflows were originally installed on the sewer network to protect homes and businesses from flooding during heavy rain. So whilst dry years like 2025 mean storm overflows are needed less often, performance last year was better than in 2022 when rainfall levels were similar, indicating that the investment delivered so far is already delivering improvements.

How Anglian Water cut overall spill duration by more than 80% in 2025

Whilst long term investment will be needed to meet the aim of ensuring storm overflows will no longer be required by 2050, Anglian Water has already removed 340 storm overflows from its network entirely, and set out detailed improvement plans for each of the company’s 1,442 storm overflows to significantly reduce discharges.

As part of its 2020 to 2025 AMP8 business plan Anglian Water invested almost £100 million to construct and upgrade 112 storm tanks across the region. This has helped to reduce storm overflows from Water Recycling Centres by creating storage to hold excess flows during heavy rain, reducing the need for storm overflows to be used as emergency release valves to prevent flooding.

This, combined with work to reduce rainfall entering the system in the first place and improvements to monitoring and prediction technology, has helped to drive last year’s best ever performance.

Lizzie Frost, Head of Catchment Flow Compliance for Anglian Water, said:

“We know our customers and communities feel strongly that storm overflow discharges are unacceptable, and we agree. Storm overflows have been part of the sewer system for decades, and they were originally designed to protect homes and businesses from internal sewer flooding during heavy rainfall – something they still do today. Our long term goal is to completely stop using storm overflows, but getting there isn’t something we can do overnight.

“We’re investing more than ever before to reduce storm overflow discharges. £1 billion of our £11 billion 2025 to 2030 business plan has been earmarked specifically to tackle storm overflows and improve river water quality. The dry weather has helped our performance, but it is not the main reason. While lower rainfall over the summer meant storm overflows were needed less often, performance was still better than previous years when we’ve had similar levels of rainfall.”

What’s next for 2026?

By the end of next year, Anglian Water will have almost 65,000 state-of-the-art AI sewer monitors installed across its network. These can predict and prevent issues like blockages before they cause an issue. So far these have prevented over 2,500 blockages in targeted areas. In the Anglian Water region, 80% of sewer flooding incidents are caused by blockages, many of which are the result of unflushable items entering the sewer system.

Anglian Water will invest £47 million to build 35 new storm tanks across the East of England. These new tanks will significantly increase stormwater storage capacity, meaning sites can store excess flows during heavy rainfall to be treated later. This will prevent untreated water from entering rivers and coastal areas, protecting the East of England’s precious natural environment.

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