<prompt> Hardness of drinking w ater should be?3l3-Jan6  <response>: Ans. is c i.e., 1-3 o Drinking water should be moderately hard 1-3 meqLit Park 2laep. 672o Softening of water is recommended when the hardness exceeds 3meqL 150 mgL.Hardness of watero Hardness of water is defined as the soap-destroying power of water,o Water is considered to be bard if large amounts of soap are required to produce lather.o The hardness is caused by high mineral content, Mainly calcium and magnesium cations,o Hardness may be : -i Temporary Carbonate hardness - Calcium bicarbonate Magnesium bicarbonate. It is called temporary because it can be removed by boiling or addition of lime.ii Permanent Non-Carbonate hardness - Calcium Sulfate, magnesium sulfate, Calcium chloride, magnesium chloride It is called permanent because it cannot be removed by boiling,o Hardness is expressed in terms of mili-equilents per litre mEqL.o One mEqL of hardness - producing ion is equal to 50 mg CaCO3 50ppm in one litre of water.Classification of hardness in waterClassificationLevel of hardness mEqjlitrea Soft waterb Moderately hardc Hard waterd Very hard waterLess than 1 50 mgL1-350- 150 mgL3-6I50-300mgLOver 6 300 mgL 