An amount of 20 gms of bleaching powder is required to disinfect 100 gallons of water.the measured quantity should be first mixedproperly with 5 gallons of water in a bucket and the solution should be allowed to settle. The supernatant solution should then be added in well or in the reservoir with vigorous stirring. atleast 1/2 an hour contact time should be allowed before the water is used for drinking purpose. The residual chlorine should always be maintaned at 0.2 to 0.3 ppm in the reservoir or well water.
Note : sample which are found to be bacterologically unsatisfactory should be disinfected as per this chlorination procedure.