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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
Sajan sarthak Best Answer
Hardness is caused by compounds of calcium and magnesium, and by a variety of other metals. General guidelines for classification of waters are: 0 to 60 mg/L (milligrams per liter) as calcium carbonate is classified as soft; 61 to 120 mg/L as moderately hard; 121 to 180 mg/L as hard; and more than 180 mg/L as very hard. BELOW picture you can see hard calcium stone buildup in side a iron pipe