How the sewer network works
In total we take 3.1 billion litres of wastewater away from homes and businesses every day, including drainage from roads, highways and public spaces.
This water flows through approximately 93,000km of pipes and goes to our treatment works, of which we have more than 1,000.
Combined sewer systems in England transport rainwater runoff and wastewater, including sewage, in the same (combined) pipe to a sewage treatment works.
The combined sewer network is meant to accommodate some storm-water runoff, but not large amounts. When more storm and ground water enters the sewer system than the pipes were designed for, storm overflows act as relief valves to avoid homes and properties being flooded.
Combined sewer networks
Overflows are part of the system designed to help protect homes from flooding in heavy rain. Most of the time they're not activated. This shows how they work.
Normal rain
Heavy rain
The types of storm overflow
There are two main types of storm overflows:
Investing to improve river health across the region
As part of our Get River Positive Pledge to ensure storm overflows and sewage treatment works do not harm rivers, we will invest over £4.4 billion on storm overflows to help improve river health across our region.
Over the next 25 years, we’re looking to make improvements affecting 2,472 storm overflows, ranging from increased capacity of storage tanks to introducing nature-based solutions.
The improvements, which will be split across our counties, form part of our Storm Overflow Action Plan (SOAP). The plan, which we’ll regularly update as we make improvements, will reduce the number of spills into watercourses across the region.
By 2040, no overflow will spill more than 10 times in an average year in high priority areas. And by 2045, this will be the case in all areas, five years ahead of Government targets.