1423. The overflow rate for plain sedimentation tanks is about__________________? September 7, 2025 by Admin A. 500 to 750 litres/hour/ m2 B. 1000 to 1250 litres/hour/ m2 C. 1250 to 1500 litres/hour/m2 D. 1500 to 2000 litres/hour/m2 ✅ The correct answer is option A.