fact sheet: More about hard water

There are two types of hard water: temporary and permanent.

Temporary hardness is the name given to water whose hardness can be removed by boiling the water. Temporary hard water forms when rain water flows over limestone and chalk rocks and reacts to form calcium hydrogencarbonate.

If rain water flows over rocks containing a mineral called gypsym, it will pick up different compounds, such as calcium sulphate. If water contains calcium sulphate then it is called permanently hard water.

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