Hardness is determined by the level of naturally occurring calcium and magnesium compounds in your water. High content classifies your water as hard, and low traces of the compounds make your water soft.

How is hard water created?

Hard water is found in areas which have a chalk and limestone geology. As water passes through the rock it picks up chalk carbonates, the concentrations of which will determine the level of hardness.

All supplies in the Thames Water area are generally classified as hard. There is some variation in the degree of hardness across the area, with water in the Guildford region being the softest. 
You can find out the water hardness level for your area by entering your post code online.

Check the water quality in your area

Is hard water harmful?

There is no health risk associated with hardness.

However, hard water can lead to scale forming and may also affect the appearance of hot drinks, increase soap consumption and reduce detergent efficiency.

If your pipework at home contains either copper or lead pipes then the minerals in hard water can create an internal protective film. This protective film can line the pipes and prevent the metals filtering into your drinking water supply.

How can I reduce the effects of hard water scale?

If hardness scale becomes a problem there are a number of simple measures that can be taken to reduce the level of deposition:

  • Reducing the temperature of your hot water to 60°C or lower to decrease the build up of scale  
  • Place a stainless steel wire scale collector in your kettle to  reduce scale build-up. 
  • Avoid scale floating on the surface of your water by regularly rinsing your plastic kettle 
  • Follow the manufacturer’s instructions for any appliances that use water.
  • Install a water softener. On occasions sodium levels within softened water can be higher than normal. We therefore do not recommend that softened water is used for drinking purposes.

The softener should be plumbed in after the drinking water point to ensure you have a separate un-softened supply for drinking.