Services · 7 min read
Sizing the water tank and pump for a G+1 house
A useful first-pass method for storage, head and flow — and the site details a plumber still needs before selection.
Reviewed August 2026
Estimate daily demand first
Start with the number of regular occupants, fixture use and reliability of the incoming supply. Storage is usually split between an underground sump and an overhead tank so the house retains gravity supply during a short power or pump interruption.
Head is more than building height
The pump must overcome the vertical rise from the lowest water level to the tank inlet, pipe friction, fittings and the operating requirement at the outlet. A pump selected only from the number of floors may be noisy, inefficient or unable to deliver the expected flow.
Details to give the supplier
- Lowest sump water level and highest tank inlet level
- Pipe material, diameter and approximate run
- Number of bends, valves and non-return fittings
- Required tank refill time
- Available power supply and preferred controls
Build in maintenance access
Provide isolation valves, a removable strainer, accessible controls and enough room to service the pump without dismantling surrounding work. Tanks need secure covers, washout access and an overflow routed where a leak will be noticed.