asked Her Majesty's Government:

With reference to the Water Supply (Water Quality) Regulations 2000 (Amendment) Regulations 2007 (SI 2007/2734), under what regulations and at what intervals water undertakers and licensed water suppliers test for the presence of substances harmful to health which may have been deliberately introduced into the water supply. [HL799]

The Water Supply (Water Quality) Regulations 2000 and the Water Supply (Water Quality) Amendment Regulations (SI 2007/2734) require water undertakers and licensed water suppliers to undertake monitoring and carry out a risk assessment for hazards. This risk assessment will be carried out in accordance with guidance to be issued by the Drinking Water Inspectorate which will follow the internationally recognised World Health Organisation water safety plan approach. For any given water supply the risk assessment will inform the controls that water undertakers and licensed water suppliers will be required to have in place, including the substances and organisms to be monitored. It is the Government's policy not to discuss security arrangements for water supplies.