Hard water is water which contains dissolved chalk, lime and other minerals. Rainwater is naturally soft, but as it percolates through chalk and limestone in the Earth, it dissolves and collects these minerals. Rainwater which falls on hard rock remains naturally soft. The hardness of the supply of mains water to your home is dependent on where you live and the source (river or ground water) of your mains water supply.
Generally speaking, hard water is supplied to 60% of homes in the UK: especially in London and the east coast. Each of these British homes require a water softener to obtain soft water for their daily use. Water quality information, including hardness levels, for individual water supplies are available through means of water testing. The Hard Water-Soft Water Map gives us an indication of water hardness in the different regions of the UK.
Each year, in a Hard Water area (300mg/l of calcium carbonate equivalent) the average family home will use water containing 70kg (154lbs) of scale. Unchecked, it will cause damage and expense. It is estimated that an ion-exchange Water Softener could save in the region of £180 for this average 4-person household.