Minimum recommended dose of "free" residual chlorine in water for routine chlorination (in mg/L)-
0.5 mg/L for a contact period of 1 hr. 0.5 mg/L for a contact period of 1/2 hr. 1.0 mg/L for a contact period of 1 hr. 1.0 mg/L for contact period of 1/2 hr.\