Most of the water in S and E England is hard. The cause is the presence of dissolved salts of calcium and magnesium, in the presence of soap a curd or scum is formed.Bathroom and kitchen fixtures are stained, washed woolens are matted and soap does not lather properly.
The serious problem starts when the water is heated above 40 degrees Celsius. Kettles develop fur and hot water pipes develop scale. This scaling increases the cost of running the system and can cause damage to the boiler and immersion heater. Proprietary descalers are available for kettles and the hot water system can be descaled by putting chemicals into the cold water cistern.
It is much better, however, to avoid scaling rather than trying to cure it. Install an Indirect cylinder to replace a Direct one, and avoid water temperatures appreciably over 40 °. A number of chemical water softeners are available, but the most satisfactory solution is to fit a water softener. This works on the ion exchange principle, sodium being added to the water in exchange for calcium and magnesium. It must occasionally be regenerated by adding salt. The unit should be fitted to the rising main above the cold water tap in the kitchen by the plumbers.