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This Briefing Paper provides information for England and Wales, unless otherwise stated. Some further information and resources for Scotland and Northern Ireland is set out in Section 6.

What is sewer flooding?

Sewer flooding is when sewage or foul water leaks from the sewerage system (through pipes, drains or manholes) or floods up through toilets, sinks or showers inside a building.

According to the performance data for water and sewerage companies in England and Wales on Discover Water, in 2015-16: 37,434 areas were externally flooded by sewage; and 4,344 properties were internally flooded by sewage.

Why does sewer flooding happen?

It may occur for a number of reasons, including a failure of the sewerage system; a blockage in the drainage pipes; or when the sewerage system is too small to take the amount of sewage and/or water entering the system. The latter in particular means that sewer flooding can be a more frequent event during bad weather, for example when too much rainwater enters the sewers from surrounding roads, houses and land.

Who is responsible for dealing with sewer flooding?

Responsibility for sewer flooding depends on which element of the sewerage system is causing the problem. In general:

  • Sewerage companies are responsible for the public sewers and drains located outside the boundary of a property;
  • Property owners are responsible for the drains and private sewers which carry their waste to the public sewer, usually up to the boundary of the property;
  • Local authorities and the highways agencies are responsible for highways drainage on the roads they maintain.

What to do if sewer flooding occurs?

If sewer flooding occurs the action that can be taken to address the problem will depend on the cause of the flooding:

  • If the problem has been caused by a blockage or other problem which is the property owner’s responsibility, they will need to address the problem themselves. They may be able to make a claim on their home insurance policy to cover the cost of any repairs—flooding should be reported immediately to the insurance company.
  • If the problem is with the public sewer or any drains which fall within the responsibility of the sewerage company, the affected individual should contact the relevant company immediately to report the problem. In certain circumstances a customer may be entitled to a compensation payment from the company.

Longer term approaches to sewer flooding

Sewage treatment and water quality is regulated at an EU level through Directives which aim to improve the water environment and protect the environment from adverse effects of urban waste water. The Environment Agency/Natural Resources Wales (the environmental regulators) can issue fines for unlicensed sewage discharges; and Ofwat (the economic regulator) can penalise companies for poor environmental performance, including persistent sewage pollution incidents.


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