Drinking water quality

We use the same water today that was on the planet billions of years ago – it just gets recycled.

Although water covers three quarters of the Earth's surface, around 97% is salt water and 2% is frozen – leaving only 1% available as fresh water. Nature recycles this 1% through the water cycle: 

  • water evaporates from seas (leaving the salt behind)
  • fresh water evaporates from rivers and lakes
  • trees ‘breathe out’ water vapour through their leaves (transpiration)
  • all the water vapour rises into the sky
  • as the vapour rises, it cools and condenses to form clouds
  • the tiny droplets that form the clouds group together as bigger droplets
  • when these bigger droplets get too heavy, they fall back to the earth as rain, snow or hail
  • some rainwater feeds plants, trees and animals. Other rainwater soaks into the ground and flows into rivers
  • rivers take water back out to sea where the cycle begins again.

Where our water comes from

Rainfall is the primary source for public water supplied in the UK. There are three categories of source water: groundwater, upland catchment water and lowland river water. The level of treatment required to meet quality standards depends on source water quality - follow the link to find out more about how we treat water.

How water gets to your property

We transport water through pipes running from rivers, reservoirs and underground sources to water supply works for cleaning. Then, it's either pumped, or flows by gravity, through a vast network of water mains to homes or businesses.

Along its route through the network, the water is stored inside closed tanks called service reservoirs. These reservoirs ensure that there’s always an adequate supply of water available to meet fluctuations in demand. They also provide extra storage if the flow of water is interrupted, which sometimes happens during maintenance work.

The network provides enough pressure to enable us to use our showers, washing machines and dishwashers. In an emergency, if possible, we can also keep the water flowing by redirecting supplies from neighbouring water distribution networks.