The simple definition of water hardness is the amount of dissolved calcium and magnesium in the water. Hard water is high in dissolved minerals, largely calcium and magnesium. In most of the textile industries, they collect water from the Underground.

Water hardness divided into two ways-1.Temporary harness, 

2. Permanent hardness. 

1. Temporary Hardness: 

Temporary hardness is caused by calcium or magnesium hydrogen carbonate.

So, to make Temporary water to soft water, we can boil this water or take the help of the following reactions:

Ca(HCO3)+Ca(OH)2→2CaCO3↓+2H2O

Mg(HCO3)2+2Ca(OH)2→2MgCO3+2H2O

MgCO3+Ca(OH)2→Mg(OH)2+CaCO3

2. Permanent Hardness : 

Permanent hardness is caused by calcium or magnesium sulphate.

So, to make Temporary water to soft water, I can take the help of the following reactions:

CaSO4+Na2CO3→CaCO3+Na2SO4

MgSO4+Na2CO3→MgCO3+Na2SO4

MgCO3+Ca(OH)2→Mg(OH)2+CaCO3