Water Storage Tank Calculator (Sump & Overhead)

Every building requires adequately sized water storage to handle supply interruptions and peak demand periods. IPC (Code of Basic Requirements for Water Supply) specifies the minimum daily water demand per capita for different building types. IPC requires a minimum storage of 24 hours of total daily demand between the underground sump and overhead tank.

IPC mandates that the sump and overhead tank together store a minimum of 24 hours of total building demand. In areas with unreliable supply (common in many US cities), engineers typically design for 48 hours of storage. The overhead tank must be located at sufficient height to maintain minimum 7m head at the lowest floor water outlet. Pumping is required from sump to overhead tank - size the pump for the total static head plus friction loss in the rising main.

Example: A residential apartment building houses 150 people with a municipal piped supply (IPC norm of 135 L/person/day). Daily demand = 150 × 135 = 20,250 L (20.25 KL/day). Per IPC storage split: underground sump = 2/3 × 20.25 = 13.5 KL, overhead tank = 1/3 × 20.25 = 6.75 KL. Rounding up for standard tank sizes, the design adopts a 14 KL sump and a 7 KL overhead tank, giving the mandatory 24-hour total storage. Fire water reserve is sized separately per IPC.