_The presence of calcium & magnesium in water commonly called “hardness” is the main cause of scale deposits on surfaces and inside tissue fibres.

Rainwater is naturally soft but once it has fallen it percolates through the soil and rocks.  Rainwater which falls on chalk and limestone dissolves and collects hardness minerals but when it falls on hard rocks such as granite it remains naturally soft.  The hardness of your water is therefore dependent on where you live in the country.