<prompt> Recommended minimum amount of Residual chlorine in drinking water is2 ppm0.5 ppm1.5 ppm4 ppm  <response>: Free Residual chlorine act Chlorine water It combines with impurities and Sestroyes them by formation of hypochlorous acid Which causes 90 of disinfection After all impurities are destroyed we leave some Extra chlorine in the water So that water remains safe and clean to drink for next 24 - 48 hrs. This additional chlorine is known as free or residual chlorine Recommendation free residual chlorine - In drinking water 0.5 mg L ppm - In swimming pools 1.0 mg L - For killing cyclops 2.0 mg L Chloroscope is use to estimate free residual chlorine level - Test used is ohotulidire test 