Causes of hard water

Rain water dissolves sulphates, chlorides and carbonates of calcium and magnesium present in many rocks. These salts cause hardness of water and also dissolve carbon di-oxide from air which converts the carbonates of calcium and magnesium into bicarbonates. These bicarbonates are able to dissolve in water causing hardness. The hardness of water is of two types: temporary hardness and permanent hardness.

Temporary hardness is due to the presence of bicarbonates of calcium and magnesium in water. These salts are soluble in water and exist in the form of positive and negative ions. The name temporary is given to this type of hardness because these ions are removed merely by boiling. Temporary hardness is removed by boiling water. Due to this calcium and magnesium bicarbonates are converted into insoluble carbonates which are easily removed.

Permanent hardness is due to the dissolved chlorides or sulphates of calcium and magnesium. These salts cannot be decomposed by boiling and hence the name permanent is given to this type of hardness. These salts are soluble in water and produce corresponding ions in solution. Both temporary and permanent hardness can also be removed by ion exchange method which involves the replacement of an ion by another.

More than 60 percent of the earth's water is groundwater; it travels through rock and soil picking up minerals, including calcium and magnesium along the way. These two contaminants produce what is commonly referred to as hardness in water.

In areas where the water is hard or very hard the local water utility may soften the water slightly but is still considered moderately hard. Consumers may still wish to soften the water further. The most common option for consumers is ion exchange water softening in the home. Household softening systems makes more economic sense because it only softens the water to be used for laundering, cleaning, and other home uses. Softening at the central or community treatment facility is costly because it softens all water including water used for fighting fires and cleaning streets.