DWI issued on 7 August new guidance on arrangements for compliance with the requirements of regulations 27 and 28 of the Water Supply (Water Quality) Regulations 2000 (2001 in Wales) (Amendment) Regulations 2007. The Amendment Regulations came into force on 22 December 2007. Regulation 27 requires water companies to carry out a risk assessment for each of its treatment works (including the water source and catchment) and the connected supply system. Regulation 28 requires water companies to provide to the Secretary of State (in practice the Drinking Water Inspectorate) a report of each Regulation 27 risk assessment and any subsequent review of the risk assessment. The Inspectorate has specified that risk assessment methodology used by water suppliers must be based on the water safety plan approach published by the World Health Organisation (WHO) in the Guidelines for Drinking Water Quality 2004 taking account of subsequent updates and associated guidance manuals published by WHO.

http://www.dwi.gov.uk/regs/infolett/2008/info0708.shtm