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Drinking water quality in England and Wales is regulated by the government through the Drinking Water Inspectorate (DWI).

The Inspectorate was set up in 1990 after the water industry was privatised to operate an independent body with staff experienced in all aspect of water supply. The DWI task is to monitor and check the safety of drinking water.

Its main job is to check that the water companies in England and Wales supply water that is safe to drink and meets the standards set in the Water Quality Regulations. Inspectors carry out technical audits of each water company. These have two main parts:

  • an annual assessment of the quality of drinking water supplied by the companies
  • inspections of the individual companies

The assessment of water quality is based on information received regularly from the water companies.

This information includes the results of the millions of tests made each year to see if the water meets the standards. The DWI check the test results against the standards. It also carries out inspections to be sure that the results are reliable and give a true picture of the quality of the water supplied.