An investigation has revealed more than 200 household appliances have been pouring filthy water into waterways because of plumbing mistakes.
The probe was launched in 2014 by Thames Water to trace the source of the dirty water that was flowing into Yeading Brook and the River Crane in Hillingdon after the water quality started having an impact on wildlife.
Officers from the Environment Agency (EA) suspected the cause was houses with bad plumbing that connected wastewater pipes to the surface water pipe network, meant for rain water.
Thames Water explored the plumbing of thousands of homes in Hillingdon and found waste water from 100 homes was flowing into the brook and the river.
After discovering the problems Thames Water has helped the homeowners to get their pipes properly connected as most people were willing to help.
However, some have refused and they have been reported to the council who can force home-owners to fix the problem.
'No one wants toilet water emptying into waterways'
Ruta Akelyte, from Thames Water's environment team, said: “No-one wants toilets emptying directly into their local waterway so it's a great feeling to have sorted this problem out and improved the water quality in the brook so much that wildlife can now easily survive there.
“We've got a massive job still to do to trace more of these mis-connections 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.”
Environment officer at the EA, Matthew Reed, said: “Vigilant members of the public alerted us to the issues and Environment Agency investigations prompted the clean-up of the brook by Thames Water.
“Washing machines, showers, and toilets were regularly discharging into the watercourse and reducing the water quality for the wildlife and creating an unpleasant environment in the brook.”
The River Crane is a tributary of the River Thames and runs for around 8.5 miles through west London.
Its source is Hayes and it follows a semi-circle towards Cranford and Heathrow before winding up in Isleworth.
The river faced sewage water leaks in September in Hounslow.
Keep up to date with the latest news in west London via the free getwestlondon app.
You can even set it to receive push notifications for all the breaking news in your area.