<prompt> The minimum recommended conecntration of free chlorine mgL in drinking water at the end of 1 hour is -0.10.511.5  <response>: Recommended contact period of free residual Chlorine in water : 1 hour Level of free residual chlorine FRC recommended : Water type Residual chlorine level Recommended Contact period Drinking water 0.5 mg per litre ppm 1 hour Water bodies, post disaster 0.7 mg per litre ppm 1 hour Swimming pool sanitation 1.0 mg per litre ppm 1 hour Ref: Park 25th edition Pgno : 752 