What are storm overflows?

Storm overflows operate as relief valves built into the combined sewer system. They discharge excess sewage and rainwater to rivers, lakes, groundwater or the sea, when the sewer system is under strain. This protects properties from flooding and prevents sewage backing up into homes, businesses and streets in response to rainfall or snowmelt. The Environment Agency sets strict protective permits to limit the impact of storm overflows on the environment.

Event Duration Monitoring-Storm Overflow-Start/Stop Detailed Data

This Water Company data shows storm overflow event duration monitor activations. The activations are recorded at the start and the stop of each potential discharge. The data has not been subject to any formal verification by the Environment Agency. The data covers all 10 water and Sewerage companies that operate in England. The data is split into Water Companies and each spreadsheet covers one calendar year.

Access the data here

Event duration monitoring (EDM)

This records the frequency and duration of storm overflow spills. They are the primary source of data on the performance of storm overflows.

Storm overflows discharge reduction plan

Defra's storm overflows discharge reduction plan sets stringent targets to protect people and the environment.

Tackling storm overflow discharges

In a sewer pipe on the River Tame in the West Midlands is a small blue box, a key piece in the puzzle to tackle sewage spills.