: Soap is wasted when using hard water for washing clothes or laundry. Because foam is not easily formed in hard water. When hard water is used in the boiler, a coating of insoluble solid metal salts is formed inside it. Such linings are called heat conductors which increase fuel consumption. Hard water cannot be used in paper , artificial silk and dyeing industries. The presence of soluble ferrous salts in hard water causes brown spots on paper and synthetic silk, and the reaction of hard water with dyes used for dyeing cloth or yarn results in insoluble matter. The result is a waste of color. Rice , pulses, etc. are not easily cooked in hard water and the taste of vegetables is less. The color of the curry turns black. Brown stains on glass and utensils.