Every storm overflow across the water network in England is now monitored - 100% of storm overflows have now been fitted with Event Duration Monitors (EDMs) to meet the target set by the government to do so by the end of 2023.

Event Duration Monitors increase transparency by measuring how, when and for how long a storm overflow is in operation. This shows when discharges are happening – it should also help the government and regulators to better hold water companies to account for illegal sewage spills and improve knowledge of overflow operation to identify where improvements can be made.

Environment Agency Executive Director John Leyland commented:

“After eight years of work, every storm overflow is now monitored, giving us much more information about where and when storm overflow discharges are happening.

“This increased transparency will allow the Environment Agency to better tackle illegal discharges from storm overflows. We are dedicated to investigating those that breach their strict permitting conditions.

“We take our responsibility to protect the environment very seriously. We are also strengthening our regulation by expanding our specialised workforce, increasing compliance checks, and using new data and intelligence tools to inform our work.”

Storm overflows are an automatic safety valve that release excess pressure on the network from flooding and heavy rain – preventing sewage backing up into properties and stopping widespread mains pipe bursts across the country.

They should, however, only be used under strict permit conditions. Increased monitoring will give government and regulators the information they need to take action when permits are breached.

In 2010, just 7% of storm overflows had monitors fitted - the installation of monitors then accelerated under the government in 2013 when Lord Benyon instructed water companies to increase their storm overflow monitoring.

Water UK Chief Executive David Henderson said:

“With 100% of the near 15,000 storm overflows across England now monitored we have the best, most comprehensive and accessible monitoring system in the world. This data will be invaluable in ensuring investment is targeted at those sites which urgently need improvements.

“Storm overflows are a design feature and act as a release valve after heavy storms. Water companies want them to operate as little as possible, which is why we are seeking regulatory approval to invest £11 billion over five years – three times the current rate – to increase the capacity of our sewers and prevent much more storm water entering the system in the first place.”

As part of the Government’s Plan for Water, over £2.2 billion of new, accelerated investment is being directed into infrastructure to improve water quality and secure future supplies, with £1.7 billion of this being used to tackle storm overflows to cut over 10,000 discharges.

This builds on stringent targets on water companies to reduce storm overflows, set out in the Storm Overflow Discharge Reduction Plan – driving the largest infrastructure programme in water company history of £60 billion over 25 years. This will result in hundreds of thousands fewer sewage discharges every year by 2050. The Plan frontloads action in particularly important and sensitive areas including designated bathing waters, meaning the overflows causing the most harm will be addressed first to minimise impact.

Environment Secretary Steve Barclay said:

“The completion of storm overflow monitoring is a major step forward in better protecting our precious waterways, as well as the communities and wildlife that rely on them.

“The wealth of data collected from these monitors will ensure that we know the full extent to the problem – increasing transparency, revealing the worst-offending overflows, and enabling regulators to hold polluters to account.”