Question

why soaps cannot lather in hard water?how to remove hardness of water

Answer 1

by electrolytic process or adding bliching pauder we remove hardeness of water

Answer 2

Because the calcium and magnesium salts react with the soap molecules to form long chain carboxylic salts of calcium or magnesium which does not dissolve in water. That insoluble substance is the loaf

Some of the methods to remove hardness from water are, 

Chemical Process of Boiling Hard Water.Adding Slaked Lime .
Adding washing soda