Basement Sump Pump Flow & Horsepower Calculator
Calculate basement sump pump GPM flow capacity, basin water inflow rate, 1/3 HP vs 1/2 HP vs 3/4 HP motor sizing, and vertical discharge lift head.
Calculated Results
Frequently Asked Questions
How do you measure groundwater inflow rate into a sump pit?
During a heavy rainstorm, unplug the pump and use a tape measure and stopwatch to measure how many inches water rises in the basin in exactly 60 seconds. Multiply inches by your basin's gallons-per-inch factor to get GPM.
What size sump pump is standard: 1/3 HP vs 1/2 HP?
A 1/3 HP pump typically discharges 30 to 35 GPM at a 10-foot vertical lift, adequate for mild water tables. A 1/2 HP pump discharges 45 to 60 GPM, providing the critical reserve capacity needed for torrential cloudbursts and high water tables.
Why is a check valve required on sump pump discharge lines?
A spring-loaded inline check valve prevents discharged water inside the 10-foot vertical pipe from flowing backwards into the sump pit when the pump shuts off, eliminating repetitive pump short-cycling.
How long will a 12V marine battery backup sump pump run?
A standard 100Ah deep-cycle AGM battery powers a 12V backup pump continuously for 5 to 7 hours of non-stop pumping, or up to 2 to 3 days under intermittent cycling (running 10 seconds every minute).