Chloramine has been used as a drinking water disinfectant in the U.S. in places like Springfield, Illinois, and Lansing, Michigan since 1929 2 . To disinfect your 50 gallon hot water heater requires 1.5 cups of bleach left in the tank for two hours or 3/4 cup of bleach left overnight. Chlorine alters the smell and taste of the water we drink and bathe with. Following the introduction of any chemical disinfecting agent, the water is usually held in temporary storage - often called a contact tank or clear well to allow the disinfecting action to complete. Example of a practical application. It was first used in the U.S. in 1908 in Jersey City, New Jersey 1 . The disinfecting properties of chlorine in water are based on the oxidising power of the free oxygen atoms and on chlorine substitution reactions. While chlorine provides an enormous public health benefit, it isn’t without drawbacks. When chlorine is added to water it reacts with organic material to form disinfection byproducts, which may increase the risk of certain cancers when consumed over long periods of time. Chlorine was first used as a drinking water disinfectant in Europe in the late 1800s. Basic chlorine pellets used in dry pellet chlorinators are around 70% to 75% calcium hypochlorite. A: The small amount of chlorine added to disinfect drinking water in accordance with U.S. Environmental Protection Agency (EPA) regulations is safe for consumption. A general rule of thumb to shock chlorinate and disinfect a storage tank is to mix non-scented NSF-approved household bleach (5.25% chlorine) in the reservoir at the ratio of 1 gallon of bleach for every 1,000 gallons of water (i.e., 1 quart for every 250 gallons of water). Open outlet farthest from tank and draw off water until free chlorine is detected. As such, it can be penetrated by the neutral underchloric acid, rather than by the negatively charged hypochlorite ion. The reaction between NaOCl and water produces produces HOCl, or hypochlorous acid, and sodium hydroxide, or caustic soda, as shown in the following chemical equation. The chlorine solution you pour into the water breaks down into many different chemicals, including hypochlorous acid (HOCl) and hypochlorite ion (OCl - ). The cell wall of pathogenic microorganisms is negatively charged by nature. Chlorine is the chemical most often used to keep swimming pools and Jacuzzis free of bacteria that can be hazardous to humans. Hypochlorous acid is responsible for bleach's ability to remove colour from objects and for its ability to disinfect surfaces. Chlorine- The most common disinfection method is some form of chlorine or its compounds such as chloramine or chlorine dioxide. Open tank outlet valves and reinstate electrical supply to any booster pumps. NaOCl + H 2 O → HOCl + NaOH. It is particularly important to re-activate secondary hot water pumps, as failure to do so may mean that chlorinated water does not enter the return circuit. Chlorine kills bacteria though a fairly simple chemical reaction. Regular supermarket grade bleach contains 5.25% chlorine.