A new report from the Drinking Water Inspectorate (DWI) has confirmed that drinking water in England and Wales remains among the safest in the world.

The latest Annual Report by the Chief Inspector of Drinking Water on drinking water quality in England and Wales also looks at the position after 25 years of regulation.

The water supply network in England and Wales consists of :

• 397 surface water sources
• 1981 groundwater sources
• 1249 water treatment works
• 4457 storage points
• 347,544 km water mains
• 52,113 private water supplies

In 2014 the water companies in England carried out a total of 3,853,350 tests, either at the consumer’s tap or the point where water leaves a treatment works , treated water storage reservoir or tower. Substances covered by the tests include lead, discoloured water, nitrate, hydrogen ion (pH), Trihalomethanes (THMs), cryptosporidium, e-coli and coliform bacteria. Only a tiny fraction (0.04%) of the tests failed to meet all the stringent water quality standards set by European Union and national legislation. The report reveals that in 2014 99.96 per cent of these standards were passed in England and 99.98 per cent in Wales.

The report says that very occasionally things happen that may have an adverse effect on water quality or cause consumers concern - the water companies are required by law to tell the Inspectorate about all these events. In England in 2014, there were 488 such events and 220 were risk assessed as being significant or serious requiring an independent investigation by a drinking water inspector.

In Wales in 2014, there were 23 such events and 10 were risk assessed as being significant - none were classified as serious.

The water companies are required to act on recommendations made by the inspector to prevent a recurrence. Legally enforceable Notices may be put in place to ensure that a supply is improved.

Exceptionally, where there is evidence that an offence was committed, the company may be prosecuted in court. Since its formation the Inspectorate has successfully brought 75 cases (65 in England and 10 in Wales) across the industry, the first being in 1995 (following an event in 1993).

The majority of prosecutions occurred during the first 15 years of the current regulatory regime and improvements made by the industry since mean that the Inspectorate has only found it necessary in the public interest to bring seven investigations to court since 2010.

In nearly all cases the company pleaded guilty and in some cases the Inspectorate dispensed a caution, rather than prosecute in court. Since 1990, the Inspectorate has cautioned 11 different companies on 24 separate occasions.

In 2014, there were 12 serious events in England, most of which were short-lived, the report says. These involved a range of issues including treatment failure (2), microbiological contamination or identification of Cryptospo ridium in a supply (4), chemical contamination (3), issue of boil water advice (1) and wide scale flooding (2).

Auditing the assets, procedures, data and operational processes of water companies is also an important part of the DWI’s work. In 2014, DWI carried out 419 technical audits of which 31 were deemed unsatisfactory.

 Click here to download the DWI Annual Report 2014 for England

Click here to download the DWI Annual Report 2014 for Wales