Water hardness
Our tap water comes from a range of different sources from upland reservoirs to groundwater from boreholes. This will affect the hardness of the tap water that we supply to our customers. The information below gives a summary of what water hardness is, and how to find the water hardness in your area.
What is water hardness?
Hardness is a measure of the amount of calcium and magnesium salt that is present in water.
Rainwater is naturally soft because it has no mineral content. As it seeps through the ground it can potentially pick up minerals, such as calcium and magnesium. Very small particles of calcium and magnesium(ions) dissolve into water as it passes through or over soft rocks like limestone or chalk. Hardness is made up of two parts: temporary (carbonate) and permanent (noncarbonate) hardness. When water is boiled, a portion of the hardness, the temporary hardness, forms a calcium carbonate scale, which can deposit on kettle elements as limescale. The permanent hardness does not do this when water boils and stays dissolved in the water.
Signs of hard water
Some usual signs of hard water include:
- Scaling inside kettles
- Reduced lathering of soaps, washing up liquids and washing powders
- ‘Tide marks’ on basins, sinks, baths, and toilets
- Scum on boiled water
How is hardness measured
Hardness is usually expressed in terms of the equivalent quantity of calcium carbonate in milligrams per litre or parts per million. However, it may also be expressed as Degrees of hardness in Clark (English degrees), French or German Degrees.
There are no regulatory limits for water hardness.
Water softeners
For people who receive a hard water supply, there is the potential to make use of a water softener to remove some of the hardness. This is a matter of personal choice. A softener will improve the efficiency and increase the life of appliances using hot water. It will make lathering of soap easier and reduce ‘tide marks’ on sanitary ware. Some people with skin conditions, such as eczema, have fewer problems if they use soft water for washing as it is not so “drying” to the skin. Conversely, it is difficult to wash all traces of soap away with soft water and people with allergies to soap may prefer to wash with hard water. If a water softener is installed, you will need to to ask the supplier if the softened water can be used for drinking and cooking purposes, if not you will need to maintain a non-softened supply of water
Many water softeners work by replacing the calcium and magnesium in the water with sodium. Too much sodium is a particular concern for babies, who have immature kidneys, and for those who are on a low sodium (or low salt) diet. It is recommended that softeners should be fitted after the drinking water tap to comply with the Water Regulations requirements of the Water Supply (Water Fittings) Regulations 1999. They should be maintained in accordance with manufacturers’ instructions.
When purchasing a water softener, we advise that you buy it from a reputable supplier. It should be installed only by a qualified plumber who is a member of a recognised Trade Association, such as the Institute of Plumbing. We also advise that you consider putting in place a maintenance contract to ensure the softener continues to operate correctly and does not become a hygiene hazard.
We recommend the use of plumbers listed on WaterSafe – the national register for qualified and competent installers. You can search for one here.
How can I check my water hardness?
Please see our tailored information on water hardness to your area here.
Check your water hardness and quality
Enter your postcode or find your area and check the top left corner of the map for your water quality.