How we look after your water

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Every year, we carry out over 500,000 tests on samples of water that we routinely collect from our treatment works, reservoirs and randomly selected customer properties, to ensure your drinking water is of the highest quality.

Water quality regulations

The Drinking Water Inspectorate (DWI) monitor and enforce water quality regulations on behalf of the Department for Environment Food and Rural Affairs (Defra).

Their job is to assess the wholesomeness of drinking water, and carry out audits of all water suppliers to examine all aspects of water quality, treatment, monitoring and analysis.

The quality of our drinking water is determined by standards set out in the Water Supply (Water Quality) Regulations 2000 (and associated amendments).

Find out more about the Drinking Water Inspectorate

Water Regulations Programme

The Water Fittings regulations (or Byelaws in Scotland) are national requirements for the design, installation and maintenance of plumbing systems, water fittings and water using appliances. Their primary purpose is to prevent contamination of drinking water.

Owners and occupiers of properties and anyone who installs plumbing systems or water fittings have the legal duty to ensure that the systems satisfy the regulations. In order to ensure that the Water Fittings regulations are followed, Thames Water manages a rolling programme of Water Regulations inspections.

Each year we inspect:

  • Existing commercial and industrial properties, for example, factories, schools, garages, dental surgeries.
  • New commercial and industrial buildings
  • New domestic properties
  • Where necessary we will inspect properties where there has been a water quality failure.
  • To support our inspection programme we also audit the work carried out by our Approved Plumbers to ensure that they continue to meet the standards set out in our membership terms and conditions

Drinking water standards

Our water is tested against 50 different elements to determine the microbiological, chemical, radiological and aesthetic qualities of it.

These standards are outlined in the legislation to protect public health and our compliance is monitored by the DWI.

Results from water samples collected at our treatment works, service reservoirs and customer taps are compared to these quality standards and any failures are then reported to the DWI.

Drinking water quality standards explained

Drinking water treatment

Our water goes through a rigorous set of processes at our water treatment works to ensure it is safe to drink. Various treatment processes are used depending on the type and quality of the source of water.

Find out information about the treatment works and processes your water goes through.

Drinking water treatment explained

Testing our water

Samples collected from customers properties are carried out by our authorised employees. The safety of our customers is important to us so please ensure that you are familiar with our bogus caller advice.

Once the samples have been collected they are passed to our advanced laboratory for analysis.

We employ highly trained staff with extensive analytical skills in microbiology, organic and inorganic chemistry, metals analysis and materials testing.

The laboratory and sampling teams are independently assessed and accredited by the United Kingdom Accreditation Service (UKAS).

Find out more about the United Kingdom Accreditation Service.