Corporate Responsibility

Tackling misconnected drains.

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Our customers sometimes unknowingly pollute local watercourses by misconnecting toilets, kitchen and bathroom appliances to surface water drains instead of the foul (wastewater) sewer. We estimate that as many as 60,000 properties across our region are misconnected. Property owners could face the risk of being prosecuted and fined up to £50,000 if they don’t put it right.

A polluted watercourse as a result of misconnected properties.

Across our region, there are three types of drains that take water and wastewater away from a property.
  • Foul (wastewater) drain - where dirty water from toilets, washing machines and sinks is collected and flows to our sewage works to be treated.
  • Surface water drain - where clean rainwater from roofs and ground runoff is collected and released directly into a local watercourse.
  • Combined drain - where both foul (wastewater) and surface water are collected in the same drain, which is then taken to our sewage works and treated.

Fixing the problem.

Once a contaminated outfall has been discovered (in other words, foul water is going where it shouldn’t), we can trace the pollution back to specific properties.

In 2017/18, we helped our customers fix faulty plumbing at approximately 736 properties across 45 catchment areas – a total area covering more than 42,000 properties. In these areas we identified 1,926 misconnected appliances.

We’re continuing to investigate another 101 surface water catchments, an area which covers over 134,000 properties. To date we’ve found over 2,050 properties with misconnections across these catchments. We use a range of techniques to identify misconnections - from sample analysis to simpler techniques including dye testing and placing wire cages in our sewer network to catch unwanted debris. Our best friend, however, is sewage fungus which is an easily identifiable natural indicator of pollution. Learn more by clicking on the link below:

Working with others.

Our dedicated Environmental Protection Team works with the Environment Agency and local authorities to combat the issue of misconnections.

We’ve been working in partnership with a range of organisations to proactively identify polluted surface water outfalls. We’re part of the ConnectRight campaign, working with environmental regulators, other water companies, local authorities and interested organisations, to reduce water pollution from drains and sewers.

Working in partnership with the Zoological Society of London (ZSL), volunteers armed with a specially designed pollution app have also been helping us identify polluted outfalls by capturing and sending us details of their whereabouts as they find them when walking along our watercourses on ‘outfall safaris’.

"There is no doubting the positive impact of Thames Water’s Surface Water Outfall Programme (SWOP) in improving rivers by removing sources of pollution that enter them from misconnections. Since 2016, ZSL and partners along with over 100 volunteers have surveyed 142 km of river in London and sent reports of pollution to Thames Water’s SWOP team. The surveys confirm that the extent of the pollution problem is worse than we had previously thought so, along with a host of other ways to tackle the problem such as public education, we need more of Thames Water’s SWOP work to effectively tackle this serious environmental issue."

Joe Pecorelli, Project Manager, Conservation Programmes, ZSL