Sewage discharges

This page is a short summary of the full PDF report Sewage discharges.

What are sewage discharges?

Sewage discharges are the release of raw, untreated sewage into watercourses, such as rivers. These discharges often take place through storm overflow valves, designed to release water from the sewer network when the volume of water is too great for it.

Some use of storm overflows is permitted, to avoid the sewer network becoming overwhelmed and risking sewage backing up into homes and businesses. However, it has been alleged that many water companies are using storm overflows far more regularly than they ought to.

How many sewage discharges occur?

In 2025 there were around 290,000 recorded sewage discharges from storm overflows in England, lasting around 1.9 million hours.

The overflow monitoring system started in 2016 when there were fewer than 1,000 monitors reporting data. Since then, the number of functioning monitors has increased to more than 14,000, and by the end of 2023 all storm overflows had monitors fitted.

Source: Environment Agency, Event Duration Monitoring - Storm Overflows - Annual Return (long-term trends dataset)

The increased number of monitors means that changes in the total number of spills over time will be dominated by the increased coverage of recorded data, obscuring any underlying changes in discharges.

Adjusting discharge data for the number of monitored overflows gives a better indication of trends, but it is still a limited measure and patterns are closely linked to changes in rainfall.

Source: Environment Agency, Event Duration Monitoring - Storm Overflows - Annual Returns

While the latest EDM data gives a much more complete picture of the number and duration of discharges from storm overflows, it still has limitations. These include the lack of reliable information on trends, no information on the volume of sewage discharged and that it only includes sewage discharged from permitted overflows, not any leaks from the rest of the system.

Local data

This data is also presented on the Commons Library interactive sewage discharges dashboard. This allows users to select data by constituencies, catchment areas, or water companies, and to look at details of discharges for individual storm overflows.

The Environment Agency publishes an interactive map of storm overflows, which includes EDM data for 2021 to 2025. The charity Rivers Trust produces an interactive map with the latest available annual EDM data for England and Wales and near real-time alerts.

Water companies automatically notify Surfers Against Sewage when a storm overflow discharges to beaches and the sea around the coast of Great Britain. Surfers Against Sewage use this to issue alerts as part of their Safer Seas and Rivers Service. Water companies also publish live data on their websites about overflows which are discharging or have done so recently.

The Top of the Poops website (which is supported by Surfers Against Sewage) publishes data which ranks parliamentary constituencies, rivers, beaches and shellfisheries by their annual number/duration of sewage discharges. It also publishes live data and maps on the number of overflows discharging.

What are the plans to address sewage discharges?

Sewage discharges have negative environmental and health impacts, such as altering river chemistry, making wildlife ill, and resulting in illness for people who use polluted waters recreationally, such as wild swimmers.

The Johnson Conservative Government set targets for the government, water companies, and regulators in its 2022 storm overflows discharge reduction plan (SODRP), which aimed to reduce sewage discharges. The SODRP called for increased monitoring, and set targets to reduce the use of overflows. It set out three main aims:

• Ecological: that storm overflows discharging into or near ‘high priority sites’ (for example, chalk streams) do not cause local adverse ecological impact by 2045,
• Health: to significantly improve discharges near designated bathing waters by 2035, and
• Rainfall: that by 2050, no overflow should discharge above an average of 10 times per year (over a 10-year period) or cause any adverse ecological harm.

In 2023, the Truss Conservative Government updated and extended the SODRP. The headline targets were retained.

In December 2025, the Labour Government published a progress report on the SODRP, setting out progress against the plan from 2022 to 2025. This reflected on achievements to date, and recommitted government to supporting delivery of the main targets within the plan.

The SODRP predates the broader programme of water reform, which also includes measures relevant to sewage discharges. Further measures to monitor storm overflows, as well as to increase penalties for pollution incidents, were introduced by the government in the Water (Special Measures) Act 2025. In addition to this, the government appointed Sir Jon Cunliffe, former Governor of the Bank of England, to chair an Independent Commission on the water sector regulatory system, which published its final report in July 2025. The government’s response is set out in its 2026 white paper.

All UK political parties have expressed a desire to decrease the volume of sewage entering the UK’s watercourses, but several factors (including the design of the sewage network, the regulatory process, and the enforcement capacity of environmental regulators) make this difficult to achieve.