<prompt> Residual chlorine in drinking water should be-0.5 mg L0.7 mgL1 mgL2 mgL  <response>: Ans. is a i.e., 0.5 mg L Water typeRecommendedResidual chlorine levelContact periodDrinking water 0.5 mg per litre ppm1 hourWater bodies, post disaster 0.7 mg per litre ppm1 hourSwimming pool sanitation1.0 mg per litre ppm1 hour 