Market guide
Size a sump pump from head and inflow
Use the real water path instead of horsepowerA useful sump-pump choice starts with water entering the basin and the resistance between the pump and the outlet. Horsepower and zero-head gallons per hour cannot describe that job.
01
Water
Measure inflow under real conditions
Time a known rise or pumped volume during representative wet conditions and retain a safety margin for uncertainty.
- Rate
- Record the basin dimensions, water-level change and elapsed time instead of guessing from storm intensity.
- Consequence
- A finished basement or inaccessible property may justify more margin and a separately tested backup.
02
Head
Calculate total dynamic head
Add vertical lift to losses from pipe length, diameter, fittings, check valves and the exterior termination.
- Curve
- Read delivered flow where the calculated head crosses the exact model's published curve.
- Path
- A large pump cannot repair an undersized, frozen, blocked or backflowing discharge.
03
Fit
Check the basin and electrical system
Confirm pump footprint, float travel, inlet elevation, usable cycle volume, circuit and starting load together.
- Cycling
- Too much pump in a small basin can create short cycles and extra starts.
- Boundary
- Use qualified plumbing and electrical work and the applicable permit and inspection path.
Evidence used
First-party sources behind this guide
- 01Residential sump pumps and Aquanot backup systemsZoeller · checked August 18, 2026Open source
- 02Current sump pumps and combination systemsWayne · checked August 18, 2026Open source
- 03Flood cleanup safetyCDC · checked August 18, 2026Open source