Most water supplies, whether previously filtered or not, and even if they appear perfectly clear, are most often contaminated by bacteria and pathogenic microbes dangerous to human life so they must be destroyed first before allowing them for human consumption. There are several processes for disinfecting water, but by far the most widespread is the treatment with and in operation, makes chlorine as a chlorine because it as enormous effective power to kill bacteria instantaneously even when used in minute doses. Moreover, its reliability and simplicity in handling and lower cost, both initially popular and common reagent for the sterilization of water. Its germicidal action even in small doses results in the destruction of enzymes necessary for the existence of microbic germs. It also possesses very considerable oxidizing powers which would cause the destruction of organic matter easy. Free chlorine reacts with water to hypochlorous acid which sets free the oxygen necessary to destroy these harmful organisms and thereby sterilize water in the most effective manner as shown in the following equation.