Ofwat sets out decision on unmonitored storm overflows


Ofwat has today set out measures that will penalise companies that do not fully monitor their storm overflows. 

All companies will have targets for reducing the average number of spills from storm overflows and where they do not meet those targets they will be subject to financial penalties 

Following consultation with a range of stakeholders and further analysis, Ofwat has decided that where a storm overflow is not monitored, or the monitor is not functioning correctly, Ofwat will assume the overflow has spilled 100 times a year. This is around four times the current average and double what Ofwat consulted on in May 2023. This will provide a strong incentive for companies to install and maintain their monitors and ensure they face financial consequences if they do not. 

The storm overflows targets for each company will form part of Ofwat’s price review for 2025 to 2030. They will help to drive delivery of the UK Government’s Storm Overflows Discharge Reduction Plan and the Welsh Government’s Storm Overflows Action Plan. 

Ofwat will confirm the final targets and incentives in its determinations in late 2024. 

 Chris Walters, Senior Director, Price Review said:   

“Companies need to monitor their use of storm overflows and reduce their use. Companies must now take account of Ofwat’s decision when preparing their business plans for submission to Ofwat in October 2023. We will continue to use all the powers we have to drive companies to get to grips with this issue.”   


 Ofwat has an ongoing investigation into all wastewater companies in England and Wales. The regulator is looking into how wastewater companies are operating their sewage treatment works, including whether sewage has been discharged into the environment at times when this should not be happening. The investigation – the biggest ever undertaken by the regulator – currently includes enforcement cases against six wastewater companies.