Minimum recommended level of Residual chlorine in Swimming pools is:: (A) 0.5 mg/L, (B) 0.7 mg/L, (C) 1.0 mg/L, (D) 2.0 mg/L
Answer is C. - Level of residual chlorine to be maintained for swimming pool sanitation is > 1.0 mg/L with contact period of 1 hour. - Also Remember, Free/ residual chlorine levels recommended in:- Drinking water = >= 0.5 mg/ L ; with contact period of 1 hour. Drinking water to kill cyclops = >= 2.0 mg/L ; with contact period of 1 hour.