Thames Water reveals it has been pumping sewage from a single pipe for 440 hours

The UK’s biggest water company has been discharging raw sewage for 18 consecutive days in some areas of the country - and is telling everyone about it through a live map on its own website.

Thames Water, which looks after water for 15 million people in the south of England, has been showing where “storm discharges” into watercourses have been happening.

In one area, Ball Hill in Newbury, Berkshire, storm overflows - which protect homes and businesses from sewer flooding - had been automatically discharging into the River Enborne for 440 consecutive hours as of 1pm on Friday. That is more than 18 days.

In nearby Stratfield Mortimer, a village just outside Reading, the “storm discharges” into Foundry Brook have been happening for nearly as long: 425 hours.

Neighbouring Burghfield had also seen discharges into Clay Hill Brook for the past 424 hours.

Thames Water’s live event duration monitoring (EDM) storm discharge map, which the company said was introduced in the interests of transparency, can be seen here.

Storm discharge is a mixture of rainwater and untreated sewage which is released by storm overflows into watercourses during heavy rain to prevent sewer flooding.

Thames Water says its systems are vulnerable in the winter months because “groundwater levels rise… leading to more water ending up in our sewers. This means discharges can happen after a relatively small storm.”

There is no way of finding out how much sewage has been released into watercourses.

Ashley Smith, of Gloucestershire campaign group Windrush Against Sewage Pollution, told The Guardian: “It shows the extent to which Thames Water is reliant on being able to use our rivers and streams as toilets to deal with problems caused largely by underinvestment and profiteering.”

It comes after Ofwat, the water firm watchdog, said last month that companies across the UK are failing to invest as much as they promised to fix their networks, including improving sewage treatment and reducing spills into the environment.

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The regulator said that between 2020 and 2022, 14 companies underspent their budget on improving their water network and eight companies underspent their budget for improving their wastewater network.

A Thames Water spokesperson said of the live data: “Taking action to improve the health of rivers is a key focus for us, but we also need to explain what is happening, and why. After a successful trial in the Oxford area, we have decided to provide close to real-time information about storm discharges from all of our 468 permitted locations. This is a key part of our River Health Action Plan to radically improve both performance and transparency in order to protect and improve the environment.

“We are absolutely committed to protecting and enhancing our rivers and the communities who love them, and we want to make these discharges of diluted sewage unnecessary as quickly as possible. We are the first company to provide these alerts for inland waters and this ‘near real-time’ data is available to customers as a map on our website. We want to lead the way with this transparent approach to data and the alerts will be available through an open data platform for third parties, such as swimming and environmental groups, to use.”

The company added its shareholders recently approved a £2bn spending plan for improving “outcomes for customers, leakage and river health”, and that it is aiming to reduce spills by 50% by 2030.