Need advice on pump capacity

Pump capacity for pumping water from sump to overhead tank

Dear Experts,

We are an apartment of 20 flats in 5 floors. Of late we observed that the pump takes ages (more than 7-8 hours) to fill the tank and is consuming more than 40 units per day. The height for pumping water (sump floor to overhead tank top) is around 85 feet and the tank capacity is 10,000 Liters. The existing pump is 1 hp (Single phase) with a discharge pipe of 1inch dia. What could be the root cause for such dismal performance of the pump?

Please advice us on the ways to resolve this issue. Our objective is to cut down power consumption by filling in the tank in less duration. We are also being advised to change to 2 inch pipeline and a 3 HP (3 phase) pump to solve the issue. Will it optimize power consumption?