The failing standard of drinking water in many UK homes is being caused by poor plumbing, according to the annual report from the Drinking Water Inspectorate for England and Wales (DWI).

The study has shown that almost a third of water that has failed the quality tests has come as a result of below standard fittings and poor plumbing practices in private pipes and properties after it has been transferred from the public water mains.

The DWI annual report revealed that odour, taste, nickel and lead are among the problems with the deteriorating quality of drinking water in UK homes, primarily caused by incorrect fittings and materials or a lack of protection from water ‘flowing back’ into the internal pipework from household appliances.

Marcus Rink, DWI Chief Inspector, commented: “A skilled and competent plumber using approved materials provides confidence in water remaining wholesome right up to the tap.”

The national register for plumbers, WaterSafe, has urged homeowners to only use approved plumbers to make sure that their supply of drinking water remains safe.

Julie Spinks, WaterSafe Director, said that UK water supplies are among the best in the world and the group will aim to maintain those standards by making sure that drinking water in homes is of the same standard as when it leaves the water treatment works at the water companies.

She added: “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.”

Every year, water samples are taken from customers’ taps, water mains, pumping stations, water treatment works and reservoirs to test for a number of substances which are then measured against the standards outlined by the World Health Organisation.

In England and Wales, the overall pass rate for drinking water was 99.96%.