In those places where water works cannot be constructed, water may be purified on a small scale by the following methods:
i. Distillation
This method is used in chemical laboratories and on ships. This type of water is flat and insipid owing to the escape of dissolved gases and requires to be aerated before use.
ii. Boiling
By heating water to a temperature of 100°C or 212°F, pathogenic organisms are killed and hard water becomes soft.
iii. Filters
Straining through muslin cloth is not a very hygienic method as bacteria are not removed, nor foul gases or fine solid particles. Charcoal, sand, porous iron may also be used as filtering materials.
iv. Domestic filters
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Are made of porcelain, clay and earth and moulded into candles or cylinders. The cylinder or candle becomes worn out by constant cleaning and may become inefficient gradually. It is rapid in action. The candle should be sterilized by boiling every third day.
v. Use of Chemicals
Bleaching powder and hypochlorite solutions may be used to purify domestic water supply.