Both types of water (temporary and hard) can be softened by adding washing soda (sodium
carbonate)
The added carbonate ions react with CA,MG ions to make an
insoluable precipitate of calcium carbonate and magnesium
carbonate. The ions are no longer dissolved so cant make the water
hard
Both types of hardness can also be removed by running water through ion exchange
columns.
These are sold in shops and have lots of Na or H ions and exchange them for
calcium or magnesium ions
Temporary hard water is removed by boiling
When heated, the calcium hydrogencarbonate decomposes to form calcium carbonate which is insoluable.