Testing water quality

The levels of all of the substances mentioned so far are monitored by the Drinking Water Inspectorate (DWI). Tests are carried out for each water authority at the water treatment works, in the distribution systems and at consumer's taps. The DWI checks the results of these tests and, if any problems are identified, takes action to ensure that the water company puts things right. Improvements in analytical chemistry mean that lower and lower levels of contaminants can be detected.