Water is a vital necessity for mankindit is used for drinking, cooking, bathing, washing clothes and utensils, gardening, pets, cleaning, agriculture, and boilers and water heaters. Water is almost invariably contaminated with acidity, salts, metals, color, odor, taste, and other organic pollutants like insecticides and herbicides and bacteria and microbes. Hence, one must resort to purification before consumption.

Water softener systems are ion-exchange resins that replace the calcium and magnesium salts present in hard water with sodium ions. The soft water thus obtained is good for bathing and for use in dishwashers and washing machines. Soda ash neutralizes the acidity of water and is widely used for the purpose. When the water is alkaline, one resorts to citric acid to neutralize the alkalinity.

Activated carbon filters are widely used for the treatment of water with strong smell of rotten eggs or garlic. Activated carbon filters work based on the principle of adsorption. Ultraviolet radiation has the power to kill the bacteria. UV filters use this effectively in the treatment of water. However, UV filters do not make the water soft or remove the odors.

The Reverse Osmosis (RO) system uses semi-permeable membranes for the purification of water. They filter out almost all unwanted impurities like magnesium, calcium, iron, and smelly compounds and bacteria. This process gives only about 10% of the input water. The domestic RO units usually contain a five-stage purification process: a pre-filter, a sediment filter, a bactereostatic carbon filter to remove color and odor, an ultra filtration membrane to remove bacteria and viruses, and a polisher to ensure removal of bacteria completely.

One should test the input water and take appropriate measures for purification. Also, tests should be carried out at regular intervals to ensure the systems function as per specifications.