Selecting a right sump pump size for your basement sump basin is important to ensure performance, efficiency. reliability, and longevity. Sump pump size can be determined by motor horsepower (pumping power) and flow rate in gallons per minute (GPM). 1/3 HP sump pumps are commonly used but 1/2 HP sump pumps and 3/4 HP sump pumps are used in high water flow conditions. Pump size is also important in order to optimize runtime when a battery backup system is used especially in smaller sump basins. The minimum recommended basin size is 24" deep x 18" wide.
Estimate the flow rate of the water coming into the sump pit so that the required sump pump size can be determined. Do this by measuring how much water accumulates in the sump basin in one minute when water is flowing into the basin. 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.
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Water Flow Calculation Example (24" deep x 18" wide basin):
Required Sump Pump Flow Rate: 12" x 1.1 gal x 1.5 SF = 19.8 GPM |