Thames Water has put an end to dirty waste water ending up in Wealdstone Brook as a result of a three-year project.
42 appliances, including sinks and toilets, were found to be emptying their loads into the brook, which is a tributary of the River Brent, after Thames Water started to carry out extensive work in 2013.
The detective work found that dirty water, which should have been destined for sewer pipes and the local treatment works, was actually running into drains meant only for surface water (rainwater from homes) and then into the brook.
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 362 homes south of Woodcock Park and north of Preston Hill.
This investigation found that 6% of homes were found to be connected to the wrong pipes, and by the close of the investigation in December 2015, 42 household appliances (including four toilets) were found to be emptying straight into the brook, which meanders through Woodcock Park.
To identify the problem areas, the Thames Water team hung 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.
Following the successful identification of the problem properties, Thames Water worked with home owners to make sure their pipes were properly reconnected.
Jonathan Evans, from Thames Water’s environment team, said: "No one wants toilets emptying directly into their local river so it’s a great feeling to have sorted this problem out and improved the water quality in the brook. Thankfully recent Environment Agency reports show pollution levels have significantly reduced.
"We’ve got a massive job still to do to trace more of these misconnections across our patch – so it’s really important that anyone having extensions built or carrying out plumbing work employs a reputable plumber and knows exactly where their wastewater is heading."
In all, Thames Water found ten washing machines, nine kitchen sinks, six dishwashers, eight handbasins, four showers, four toilets and one bath were emptying their loads into the brook.