The hardness of water is the total number of divalent ions present in a certain amount of water is called hardness of water. Divalent ions such as calcium ion, magnesium ion, and Fe2 ion can be found in water. The hardness of water is measured on a scale. To measure water hardness, the amount of calcium carbonate is generally measured in milligrams per liter (mg/L). On the basis of hardness of water it is classified as follows: 0 to 60 mg/L is soft ~61 to 120 mg/L is moderately hard 121 More than 180 mg/L is considered hard. More than 180 mg/L is considered very hard due to the salts dissolved in sea water. Normally the hardness of sea water is around 6,570 ppm (6.57 grams per liter) (Mohammad Rafiqul .