The 'hardness' of water depends on the amount of calcium it contains - the higher the levels of calcium, the harder the water.
Water hardness varies from region to region, depending on the amount of minerals which dissolve in rainwater as it soaks through the ground.
Most of the water we supply in southern England comes from underground chalk aquifers, so the water is hard.
This doesn't affect the quality of the drinking water or the performance of soaps and detergents, although it can lead to a build-up of limescale in kettles, boilers and hot water pipes.
Limescale is harmless but it is advisable to clean kettles and keep hot water systems below 60°C to help keep build-up to a minimum.
Some people choose to fit a water softener - these should be fitted to comply with the Water Supply (Water Fittings) Regulations 1999.
Softeners can significantly increase sodium levels in water and so one tap in a property should still supply unsoftened water for cooking and drinking.
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