Your water must be safe to drink

Drinking water must meet strict standards that ensure it is safe to drink and the quality is acceptable to consumers.

99.96% Overall performance in England and Wales (known as Overall Mean Zonal Compliance)

Results of testing drinking water against national standards for quality

Source: Drinking Water Inspectorate; England and Wales, Jan 2019 - Dec 2019

Click for company comparison Close Panel

Why might performance vary?

On average, over 99.95% of all tests pass the standards and small variations are due to local factors which can affect individual samples of drinking water. The pipe material connecting your supply can also influence water quality. Your company will provide the results of the latest tests on water in any postcode in their area and customers can also ask for a sample of water from their own home to be tested.

Overall performance against water quality tests (known as Overall Mean Zonal Compliance)

The graph shows each company’s overall performance against the water quality tests (known as Overall Mean Zonal Compliance) for the latest year.

      Overall performance against water quality tests (known as Overall Mean Zonal Compliance).

      Source: Drinking Water Inspectorate

      Overall performance against water quality tests (known as Overall Mean Zonal Compliance)

      The graph shows each company’s overall performance against the tests on water quality (known as Overall Mean Zonal Compliance) over the last three years.

          Overall performance against water quality tests (known as Overall Mean Zonal Compliance). Hafren Dyfrdwy was formed in 2018, and at the same time the area supplied by Severn Trent changed. Data for 2017 for these two companies is for the areas that were supplied by Dee Valley and Severn Trent before the changes in 2018, and the 2018 data for Hafren Dyfrdwy is for the second half of the year.

          Source: Drinking Water Inspectorate

          • Very strict standards apply to drinking water – they are set to protect public health and to ensure water quality is acceptable to consumers.

            The standards cover micro-organisms, chemicals such as nitrate and pesticides, metals such as lead and copper, and the way water looks and how it tastes. A consumer advice leaflet on www.DWI.gov.uk has more detail on national drinking standards and regulations.

            Your local water company can give you exact details of the composition of the water supplied to you.

          • Water quality events regarded as “serious significant or major” by the Drinking Water Inspectorate (DWI) include events that do, or may, affect the water quality for a number of properties and/or may, unless managed, cause concern amongst the local community. The cause of such events may be:

            • a deterioration in raw water quality, perhaps due to poor weather, which can stir up river sediment
            • things going wrong at the treatment works, perhaps a power failure, or pump malfunction
            • events occurring during the journey through the water mains, perhaps a disturbance in the water flow through the mains, (maybe a leak or burst) can disturb sediment in the pipes, which can make the water unclear.

            Companies report drinking water quality incidents to the DWI, which investigates both the cause and company action to safeguard public health. DWI ensures that any lessons are learned and best practice is followed on all occasions. It has a range of enforcement options (including prosecution) where companies have failed in their duties.

            Customers internal plumbing can also cause drinking water quality problems if not fitted or maintained properly. These events generally affect only a single property and numbers are not included in the figure above. They may include:

            • taste issues (due perhaps to pipes of the wrong material),
            • coloured water (maybe due to cross connections within the home),
            • or bacterial contamination (poor hygiene at the tap).

            Additionally, new taps may leach low levels of nickel into the supply for a period after installation.

          • There is no need to install a filter with the home as a health protection measure. By law your water company has to supply water that is safe to drink and the test results show that on practically all occasions the water passes the tests for water quality.

            Some customers choose an activated carbon filter to remove the taste and odour of chlorine - however, simply storing a covered jug of drinking water in the refrigerator will work just as well.

          • You should regularly clean your drinking water taps in your home with your normal kitchen cleaning fluid, followed by thorough rinsing. Bacteria and other microorganisms occur naturally and are found on the outside of the tap and inside the lip of the spout.

            If you change your plumbing or connect appliances to the water supply (e.g. washing machine), only use those which comply with The Water Supply (Water Fittings) Regulations (England, Wales and Northern Ireland).

          Unsure about your water quality?

          Please contact your local water company. Don’t know who your supplier is? Find out here

          Your browser is out of date!

          Please update your browser to view this website correctly.