Thames Water is making continued progress with its investigations programme to identify and remove misconnections from its network - but it is predicted that there are at least another 60,000 misconnections still to be found.

Recent initiatives include a two year campaign by the water company, the Environment Agency and Harrow and Brent councils which started in 2012 after dirty water, which should have been destined for sewer pipes and the local treatment works, was found to be running into drains meant only for surface water (rainwater from homes) and then out into Wealdstone Brook, a tributary of the River Brent.

The Environment Agency suspected that houses had incorrectly connected their wastewater pipes (for dirty water from appliances like toilets and showers) into the surface water pipe network, prompting an investigation by Thames Water into 1750 homes in the Kenton area between 2012 and 2014.
72 homes were found to be connected to the wrong pipes, and by the close of the investigation in December 2014, 339 household appliances (including 50 toilets) were found to be emptying straight into the stream.

Following the successful identification of the problem properties, Thames Water and council environment teams worked with home owners to make sure their pipes were properly reconnected. More than 60 washing machines no longer empty their loads into Wealdstone Brook as a result.

In another project which started in 2009 dirty water, which should have been destined for sewer pipes and the local treatment works, was found to be running into drains meant only for surface water (rainwater from homes) and then out into Muswell stream, a tributary of the River Lee via the Pymmes Brook. An investigation by Thames Water into 6000 homes between 2009 and December 2014 identified 448 homes which were connected to the wrong pipes, with 975 household appliances (including 26 toilets) found to be emptying straight into the stream.

Initial investigations in both projects to identify problem areas involved the Thames Water team hanging wire cages inside the drain network to catch toilet and kitchen waste and other evidence of pollution as it was flushed out of toilets and taps and along to the watercourse.

Once the hotspots were identified further detective work was carried out, including household surveys, CCTV surveys and placing colourful dye into toilets to trace where it flushed.

In the Thames Water region, plumbing mistakes result in up to one in 20 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.

The Thames Water misconnections team work in close partnership with the Environment Agency to trace and reduce the number of misconnections, but it is predicted that there are at least another 60,000 misconnections still to be found.