Thousands of incorrectly plumbed toilets, washing machines and dishwashers have been uncovered by Thames Water, saving the environment from more polluted rivers and streams.

Misconnected pipes from household appliances can allow wastewater, some of which contains dangerous chemicals, to get in to surface water sewers, which are designed to hold rainwater and drain into natural watercourses.

By uncovering the incorrectly plumbed appliances, Thames Water has removed 117 million litres of wastewater flowing into the environment every year, which is the equivalent of 47 Olympic swimming pools.

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Across the Thames Valley and London more than 8,000 misconnected appliances at thousands of properties have been identified over the past five years.

Now, the company's waste networks team is now planning to carry out more than 1,000 additional inspections across the region.

Stephen Barry, Thames Water’s environmental protection manager, said: “Household appliances which are connected to the wrong drainage pipe can have a serious impact on the environment. Most misconnections 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. Failing to do so can also lead to extremely expensive repair bills.

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“We’re pleased to have found so many of these misconnections over the past five years 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.”

Thames Water works with environmental groups, the Environment Agency and local authorities to identify points where pollution is entering waterways to spot possible misconnections.