Poor plumbing is a major cause behind drinking water failing to meet quality standards in customers’ homes.

A report has revealed that nearly a third of water that fails is as a result of poor plumbing practices and sub-standard fittings in private pipes and properties after it has been transferred from public water mains.

The Drinking Water Inspectorate for England and Wales’ (DWI) annual report found that lead, nickel, taste and odour are some of the problems deteriorating the quality of drinking water. These are caused by wrong materials and fittings or inadequate protection from water ‘flowing back’ into internal pipework from household appliances.

DWI chief inspector Marcus Rink said: “A skilled and competent plumber using approved materials provides confidence in water remaining wholesome right up to the tap.”

WaterSafe, the national register for plumbers, is urging homeowners to use approved plumbers to help keep their drinking water supply safe.

WaterSafe director Julie Spinks said: ²Water supplies in the UK are among the best in the world and we want to ensure that drinking water is as healthy when it comes out of customers¢ taps as it is when it leaves the water companies¢ treatment works and water mains.

“The use of a nationally registered plumber such as the WaterSafe scheme goes towards securing safe clean water for all, delivering the high quality of water we have come to expect.”

Each year, samples of water are taken from reservoirs, water treatment works, pumping stations, water mains and customers¢ taps to be tested for a range of substances and measured against standards set by the World Health Organisation.

The overall pass rate for drinking water in England and Wales was 99.96 per cent.