Recommended minimum amount of Residual chlorine in drinking water is

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