Water quality monitoring

The quality of drinking water in Severn Trent Water is monitored throughout various stages of treatment and distribution.  This includes source water abstracted from rivers, reservoirs and aquifers; the treatment process and finished treated water; our distribution system; and finally water at our customers taps.

The standards which we must comply with are some of the tightest in the world.  They incorporate standards from the European Drinking Water Directive and UK Legislation (National Standards).  They are set in a variety of ways; most define maximum levels, and a few minimum levels, while some state the percentage of samples which must meet the required standards.

In England and Wales the primary responsibility for enforcing the regulations is with the Drinking Water Inspectorate (DWI).  They undertake technical audits of procedures and assets, which includes management of sampling programmes and analytical laboratories.  The DWI produce an independent annual report summarising our performance against quality standards which is available online at www.dwi.gov.uk.

The monitoring programme we undertake is extensive.  It provides an important check on the quality of the water we supply, and reflects the care in which we manage and operate our treatment works and distribution systems.

In 2009, we achieved 99.97% compliance (mean zonal compliance) with quality standards at customers' taps.  In total, over 600,000 tests were carried out to monitor compliance against water quality standards in 2009.

For the small number of samples where a standard was contravened an immediate investigation was carried out and remedial actions initiated as necessary.  This includes consultation with Public Health Doctors and Environmental Health teams.  The majority of exceedances are minor or temporary in nature, and in many cases are associated with the condition or maintenance of the plumbing within an individual customers property.  All exceedances are reported to the DWI who can investigate further if they choose.

Changes in regulation mean that the current way in which our compliance is measured is not directly comparable with the years prior to 2003.  However, we are proud of a record which has shown consistently greater than 99.9% compliance with the relevant standards since 1997.

Information on the water quality in your area or fact leaflets on water quality issues are available on this website, or by telephoning us on 0800 783 4444.