Foul and surface water sewers

The foul sewer is designed to carry contaminated wastewater to a sewage works for treatment, whereas the surface water sewer carries uncontaminated rainwater directly to a local river, stream or soakaway.

What each sewer does:

Sewer system Disposes of: Transferred to:
Foul water Toilet, bath, shower, kitchen sink, washing machine, dishwasher, etc Local sewage treatment works
Surface water Rainwater from roof, driveway, patio, roads, etc Local watercourse

Across the Thames region, plumbing mistakes result in up to one in ten households misconnecting their waste appliances to the surface water system and in some parts of London this is as many as one in three homes.

As a result of these misconnections, the equivalent of 1.8 Olympic-size swimming pools of wastewater wrongly enter the region's rivers and streams every day.

We are working in partnership with the Environment Agency to reduce the number of misconnections across our region.

More information on misconnected pipes

ConnectRight is a partnership of organisations working to reduce water pollution from drains and sewers.

Find out how to check if your property has misconnected drains, what to do if you see pollution, and get further information on the ConnectRight website:

Check your pipes are connected properly and find out more at ConnectRight

Also in this section

Are you polluting? Identifying misconnections Threats to the sewer system Who is responsible?