Selecting a sump pump size for your basement can be determined by motor horsepower (pumping power) and flow rate in gallons per minute (GPM). 1-3 horsepower sump pumps are commonly used but 1-2 HP sump pumps and 3-4 HP sump pumps are used in extreme water flow conditions.
Selecting the right sump pump size is important in terms of efficiency, reliability, and durability.
Estimate the flow rate of the water coming into the sump pit so that the correct sump pump HP (Horse Power) can be determined. Do this by measuring how much water accumulates in the sump pit in one minute when water is flowing into the sump pit. The best time to do this is during a high-water flow event like a heavy rainstorm. Use a tape measure to determine the rise in water level (inches) in one minute. If you have a standard 18" diameter cylindrical sump pit, a one-inch rise in water level is 1.1 gallons. The larger the sump pit diameter the more water volume it contains.
Example (10' Vertical Lift):
Water Flow Calculation Inches of Water Level Increase in One Minute = 12 (In)
1" Water Column volume = 1.1 Gallons
Safety Factor = 1.5
Required Sump Pump Flow Rate --> 1.1 (gal) x 12 (In) x 1.5 (SF)= 19.8 GPM
Select the Right Sump Pump Size Based on the Required Flow Rate (GPM) below: