Drinking water standards explained

The quality of our water is exceptionally high, but its taste and hardness can vary depending on whether it has been taken from a reservoir, borehole or river.

Our unique Yorkshire Grid also means that water can be transported from one area of Yorkshire to another depending on where it's needed most, so your water will not always come from the same source.

The drinking water we supply is of excellent quality and is regularly tested to make sure it remains this way. In 2008 we met the required standards set by our regulator the Drinking Water Inspectorate (DWI) in 99.96% of the tests.

If you'd like to know more about how we performed in 2008 you can download a copy of our Drinking Water Quality report produced annually to meet the requirements of the Water Supply (Water Quality) Regulations 2000. 

Alternatively, you can download our Drinking Water Quality Standards Explained leaflet which summarises the various quality standards and shows you how well we performed in 2008.  

Download drinking water quality report 2008  (1.67mb)   

Download Your water quality leaflet (324 kb)

The Water Quality Regulations set a specific standard for each substance (or parameter).  Some parameters are measured in milligrammes per litre (mg/l); 1mg/l is one part in a million.  Others are measured in microgrammes per litre (µg/l); 1µg/l is one part in a billion.

Testing the water we supply

We continually monitor water from our 83 treatment plants to ensure that it meets the standards. Regular samples are taken from our 381 service reservoirs, where treated water is stored, and from customers' taps.

Samples are analysed for the substances listed in the standards. Typically over 500,000 tests are carried out each year together with many more operational checks, using state-of-the-art technology and laboratory techniques.

How the standards are set

You'll be pleased to know that the quality of the drinking water in Britain is controlled by some of the most rigorous regulations in the world. The European Union have set standards for over 50 different substances. On top of this the UK government has added their own more stringent standards which help to further protect public health.

Standards don't always relate to health; tests are also carried out to make sure our water tastes and looks ok. The Drinking Water Inspectorate(DWI) independently monitors our supply and advises the government on all our drinking water quality performance.  Visit the DWI website for more information.

What we do if standards aren't met

If we fail to meet the standards we'll always investigate. promptly to ensure there is no risk to health.  If there might be, we advise the Health Protection Agency.  We always provide the Drinking Water Inspectorate (DWI) with details of these investigations.

What we're doing to improve your water supply

We're currently upgrading water treatment works and renovating our water distribution network to reduce the risk of discoloured water and to reduce leakage. This will bring further improvements and benefits to you and our environment.

See how we're improving your water supply

What's in your water?

Water contains a variety of naturally occurring minerals and organic substances. During treatment we add a number of chemicals (approved by the Regulations) to ensure the water is free from substances and organisms that may be harmful to health. We monitor our treatment works 24/7 to ensure our water continuously meets the standards.

Find out more about what's in your water