Storm overflow investment

We are committed to progressively eliminating the discharge of untreated sewage into rivers and the sea and are investing more than £3 million a month to tackle storm overflows.

Where we are investing

From 2020 to 2025, we are spending £150 million on storm overflows to reduce their impact on the environment.

This number could more than double between 2025 and 2030 if our business plan is approved by our regulator.

We are currently investing in the following key areas.

Increasing treatment capacity

We are making improvements to our water recycling centres to increase their capacity to treat wastewater.

This will help to ensure more wastewater can be treated during wet weather before it is safely released back into the environment.

Installing storage tanks

During periods of heavy rainfall, we cannot always treat the high levels of wastewater that enter our water recycling centres, causing overflows to operate automatically.

To tackle this issue, we are constructing storage tanks that will hold the water until nearby water recycling centres can treat it.

Separating rainwater and foul water

Many of our older sewers carry both rainwater and foul water together, which puts unnecessary stress on the network.

While it isn’t practical to replace all these sewers, where possible, we are carrying out schemes to separate rainwater and foul water.

Using nature-based solutions

We use nature-based solutions, such as wetlands and reed beds, where possible to treat discharges from storm overflows before they are released into the environment.

These solutions are a more environmentally friendly alternative to constructing large treatment works or tanks, which often require lots of energy.

Lining and sealing pipework

Groundwater is held within rocks and soil and when levels are high it can get into sewer pipes through small cracks – this is known as groundwater infiltration.

This puts stress on the network and can contribute to storm overflows operating, which is why we line and seal ageing pipes every day.

Investment schemes from 2022 to 2025

  • 16 schemes to increase treatment capacity at our sites
  • 31 schemes to install stormwater storage tanks
  • 1 scheme to separate surface water and foul water
  • 30 schemes to treat discharges using nature-based solutions
  • 23 schemes to line and seal pipework on our sewer network

Storm Overflows Improvement Dashboard

Our dashboard shows which overflows are currently being addressed, and where investment is needed for us to meet new government targets.

Get updates about storm overflows

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Storm overflow

National Storm Overflow Plan for England

Storm overflows are an international issue, although England is leading the way, having monitors on all overflows and an investment plan that covers the whole country.