For disinfecting water stored in tanks and sumps, add roughly 50 ml of sodium hypochlorite 5-6% for every 1000 litre of raw water. The water will be devoid of bacterial contamination if the treated water has residual chlorine presence up to 0.5 ppm. Increase or decrease the dosage levels depending on the presence of residual Chlorine in the treated water. Ensure that the treated water has Chlorine smell and presence of at least 0.5 ppm as excess / residual Chlorine.