Social & Preventive Medicine Residual chlorine in chlorination of water should be: A 1 mg/L after 1 hr B 0.5 mg/L after 1 hr C 1 mg/L after 30 mins D 0.5 mg/L after 30 mins 💡 Explanation Residual chlorine in chlorination of water should be: ✓ Correct Answer: B. 0.5 mg/L after 1 hr