From its origins in a raincloud, every drop of water has made its way through the vast stores of water, above and below ground. Here we detail some of the substances that are tested and the results that came from these tests.
The water is then treated until its quality is among the highest in Europe before it makes its way to your tap along some of our 13,753 kilometres of water mains.
A comprehensive testing and monitoring programme is in place throughout the treatment and supply process to make sure your water is always safe to drink.
In 2013, our scientists tested for more than 100 substances in samples taken from household taps, 90 water treatment works and 204 service reservoirs.
Water quality met the strict standards enforced by the Drinking Water Inspectorate in 99.94% of cases.
A summary of compliance with the current water quality standards is given in the annual Chief Inspector's report. You can also find out how our performance on water quality compares to other companies by visiting our Discover Water page.
Find out more about looking after water in your home.
Discover the journey your drinking water takes before arriving at your tap by watching our short film above.