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Sump Pump Runtime and Capacity Calculator
A sump pump must remove water faster than it enters while avoiding excessive short cycling. This calculator compares inflow with rated pump flow, then estimates run and refill time from usable pit drawdown volume. Actual capacity depends on discharge head, pipe, check valve, power, debris, and the manufacturer’s performance curve, not the box’s zero-head rating.
Planning estimate only. Check measurements and real-world constraints before buying materials or making a commitment.
Calculate your scenario
Change any input. Results update immediately.
Your results
Estimated pump run time
0.36 minutes
Time to lower water through the switch range.
Estimated cycle interval
1.56 minutes
Run plus refill time at steady inflow.
Flow capacity margin
27.0 gal/min
Short cycling may warrant system review.
How the calculation works
The calculator applies this relationship to the inputs above. Keep every measurement in the unit shown.
Worked example
Use this example to check the calculator by hand before relying on a result.
Assumptions behind the result
- • Inflow is steady during a cycle.
- • Pump flow is evaluated at actual head.
- • Pit area is representative.
- • Switch levels are reliable.
- • Backup power and alarm needs are assessed separately.
Mistakes that change the answer
- • Using zero-head pump rating.
- • Ignoring water entering during runtime.
- • Assuming frequent short cycles are harmless.