Hard water is the high amount of dissolve mineral or ions as calcium,magnesium etc in the water.

If i want to use hard water for my textile dye processing,then my hard water must be turned into soft water through different reactions for good results.

Water can be hard in two ways,

Temporary and permanent hardness. 

Temporary hardness is caused by calcium or magnesium hydrogen carbonet.

So, to make Temporary water to soft water, I can broiled 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

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