Water Supply Pipe Calculator

The water supply pipe calculator starts from occupancy-based demand (litres per person per day) to determine daily water demand, storage tank capacity, and the required pipe sizes for the rising main and distribution network. Based on IPC (Plumbing Services) and IPC (Basic Requirements for Water Supply and Drainage).

IPC is the primary reference for plumbing design in US buildings. Two-tank system (underground sump + overhead tank) is standard across the US due to intermittent municipal supply. Rising main pump transfers from sump to overhead tank. Pressure zones required for buildings above 6 floors. Backflow prevention: double check valves at all connections to mains. Water meters: mandatory for buildings consuming > 500 KLD.

A residential apartment building has 120 occupants at 150 L/person/day, giving a daily demand of 120 × 150 = 18,000 litres (18 kL). Following the 2-day storage rule, the overhead tank is sized at 18 kL and the underground sump at 18 kL. The overhead tank is filled from the sump in 4 hours, so the rising main flow is Q = 18,000/4/60 = 75 L/min (1.25 L/s). At a limiting velocity of 2.5 m/s, this flow requires a rising main of approximately 32 mm nominal diameter, with a transfer pump sized for this flow plus the total static and friction head.