Value of free residual chlorine in Drinking water should be:: (A) 0.2 mg/L, (B) 0.3 mg/L, (C) 0.4 mg/L, (D) 0.5 mg/L
Answer is D. It's should be minimum 0.5 mg/l (ppm) in drink water >= 1.0 mg /l swimming pool >=2.0 mg/l kill cyclops Measured by chloroscope