United Utilities cuts storm overflow spills across the North West

United Utilities has reported another reduction in storm overflow operations across the North West over the past year, demonstrating further progress on its environmental commitments. 

Reflecting targeted improvements at more than 400 storm overflows across the region, official figures released today by the Environment Agency confirmed a 22% reduction in spill numbers — the equivalent of 16,974 fewer spills — while the duration of spills also fell by 27%, amounting to 123,325 fewer hours last year.  

Storm overflow operations have now fallen for the past two consecutive years, delivering a combined 38% reduction in spills since 2023. 

While drier weather contributed to reduced spills during the first half of 2025, rainfall over the full year was 101% of the historic average in the North West. 

 Louise Beardmore, Chief Executive of United Utilities, said: “We’re pleased to show another year of progress in reducing storm overflows across the North West. The reductions we’re seeing are the result of the investment we’re making and the hard work of our teams delivering our biggest and most ambitious investment programme for over a century.” 

“Across the region, the company has been delivering a wide range of improvements, including new storage tanks to capture and store wastewater during periods of heavy rain, upgrades to wastewater treatment works, and sustainable drainage solutions which divert rain run off out of sewers and into surface water drainage systems. 

Other infrastructure improvements have included pipework upgrades and the use of AI and machine learning to identify issues such as blockages, so that proactive action can be taken before impacts occur.  

The investment supports United Utilities’ commitment to cut storm overflow activations by 60% in the decade to 2030, with the company already achieving a 47% reduction to date. 

• In Cumbria, 50 interventions across 43 storm overflows prevented 3,040 activations. For example, a new storage tank at a previously high-spilling site — Blennerhasset Pump Station — cut spills from 199 in 2024 to just 31 last year, improving water quality in the River Ellen. Interventions at Kirkbride Wastewater Treatment Works delivered a 77% reduction in spills.

• In Cheshire, interventions have strengthened network performance, with improvements at 64 storm overflows preventing 808 activations in 2025. Interventions included the inspection and cleaning of 9,488 metres of sewer, which alone prevented 192 activations.

• In 2025, 31 interventions were delivered to improve 31 storm overflows across Together, these improvements prevented 485 storm overflow activations. Interventions included the installation of an innovative WaStop nonreturn valve to prevent backflow during high sea levels, providing extra protection against tidal water entering the network. The team also carried out the inspection and cleaning of 5,564 metres of sewer.  

• In Lancashire, 1,685 overflow spills were prevented thanks to 37 interventions across 36 storm overflows. This included the deployment of five WaStop nonreturn valves, along with additional onsite storage capacity at Gisburn WwTW, Burton-in-Lonsdale WwTW, Horton-in-Ribblesdale WwTW and Wray.

• Across Greater Manchester, 129 interventions improved 125 storm overflows. These included adding extra onsite treatment capacity, enhancing automated return systems on five storm tanks, and inspecting and cleaning nine kilometres of sewer. Together, these interventions prevented 4,225 overflow activations.

Louise added: “Our investment is making a real difference to towns, cities and local communities who want to see an improved and healthier environment for the region’s rivers, lakes and coastlines. We know there’s more to do. Customers have told us that reducing the use of storm overflows is something they care deeply about, and it remains a priority for us.” 

United Utilities is investing more than £13.5 billion in the ‘Big North West Upgrade’ between 2025 and 2030. The programme will deliver new infrastructure, improve water quality, replace old water pipes, reduce leakage to its lowest ever level, and protect over 500km of rivers and bathing waters.