A partnership between a water company, charities and an army of volunteers has led to the discovery of hundreds of incorrectly plumbed appliances, which pollute rivers and streams.

Since 2016, the UK’s largest water company, Thames Water, has worked with the South East Rivers Trust and the Zoological Society of London (ZSL) to identify more than 400 misconnected appliances along the Hogsmill River in Surrey - a tributary of the River Thames that flows through Surrey and Greater London, England.

All household goods should be plumbed into the wastewater sewer network, so the water can be taken away and treated. However misconnected pipes from household appliances are not uncommon and can allow wastewater to get in to surface water sewers, which are designed to hold rainwater and drain into natural watercourses.

To tackle this issue, Thames Water funded project to raise awareness of the environmental impact caused by misconnected pipes and generate community engagement and interest in local rivers and watercourses.

Thames Water works with environmental groups, the Environment Agency and local authorities to identify points where pollution is entering waterways to spot possible misconnections. In addition a group of dedicated volunteers also conduct Outfall Safaris to spot any water pipes that could be polluting the river.

If pollution is spotted by the volunteers, it is reported and catalogued on an app, which is then investigated by Thames Water to identify the offending properties. Responsibility for fixing misconnections lies with the property owner and it is estimated that four per cent of properties in the Thames Water region have a misconnection issue.

The project has successfully identified more than 400 of incorrectly plumbed household appliances, including toilets and dishwashers. The biggest offenders are washing machines.

Richard Pumfrett, Thames Water’s environmental protection technical lead, said: “Household appliances which are connected to the wrong drainage pipe can have a serious impact on the environment. Most misconnections will have been done entirely by accident, but we would urge anyone installing a new appliance or fitting new connections to make sure they’re plumbed in properly.

“The Hogsmill Outfall Safaris have been a great way to increase awareness of the issue, while involving the local community to take stewardship and help manage this wonderful chalk stream. Through this partnership we’re pleased to have found so many of these misconnections and helped owners fix them, but we’re determined to keep doing more to ensure all wastewater is taken to our sewage works where it can be safely treated.”