The Drinking Water Inspectorate’s annual report for 2016 published today says the UK’s water supplies are among the healthiest in the world – with 99.96 per cent passing stringent standards.

However, of those which do fail, nearly a third are due to problems in people’s own homes,

According to the report, poor plumbing practices and sub-standard fittings are among the main causes of a deterioration in the quality of drinking water, after it has been transferred from public water mains into private pipes and properties.

Lead, nickel, taste and odour are behind some of the failures and these are usually caused by the wrong materials and fittings being used or inadequate protection from water 'flowing back' into internal pipework from appliances, such as dishwashers.

These are among the findings published this year by the independent regulator for drinking water quality, the Drinking Water Inspectorate for England and Wales, in its annual report.

The report covers water quality testing and results, public confidence in drinking water, events and technical audit activity for five regions in England and Wales.. It also contains a summary of all results of the water companies regulatory sampling programme and a list of all the cautions and prosecutions carried out by DWI.

The most recent prosecution undertaken by the DWI against a water company was March 2015, when (failure to operate an adequate treatment process cost Sembcorp Bournemouth Water £73,000+ in fines and costs. United Utilities was the most recent company to receive a caution in July 2013 following the investigation of an event where water was supplied from Ennerdale works to consumers in Whitehaven and the surrounding areas which was inadequately disinfected due to a lack of control of the pH of the water during disinfection.

Each year thousands of samples of water are taken from reservoirs, water treatment works, pumping stations, water mains and customers¢ taps by water companies.

These are tested in laboratories to monitor for a range of substances, including metals, pesticides and naturally-occurring bacteria which are measured against standards set by the World Health Organisation.

WaterSafe, the national register for plumbers which is backed by the Drinking Water Inspectorate and all water companies in the UK, is urging homeowners and property managers to use approved plumbers to help keep drinking water supplies safe.

Plumbers on the WaterSafe register have specific training in the Water Supply (Water Fittings) Regulations and Byelaws, which are designed to keep water in the same safe and healthy condition it is supplied by water companies, and avoid the risk of contaminated water.

Marcus Rink, Chief Inspector of the DWI, said:

"A skilled and competent plumber using approved materials provides confidence in water remaining wholesome right up to the tap. 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.”

Click here to download Drinking water 2015 Summary of the Chief Inspector’s report for drinking water in England

Click here to download Drinking water 2015 Summary of the Chief Inspector’s report for drinking water in Wales