Pool & spa
Pool Pump Size Calculator
Pump flow and size from the volume and the turnover time you want.
Result
Flow is only half the sizing question. The pump also has to overcome the resistance of the plumbing, filter and heater, and an oversized pump on undersized pipe wastes energy and can damage the filter. Many jurisdictions now require variable-speed pumps, which run longer at lower flow and cost far less to operate.
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About this calculator
How many turnovers a day does a pool need?
One is the traditional target, though modern practice favours running longer at a lower speed rather than fast for a few hours. Circulation quality matters more than the raw count.
Is a bigger pump better?
Almost never. It costs more to run, can exceed the filter's design flow, and pushes water through the filter too fast to clean it properly.
Why are variable-speed pumps worth it?
Power draw falls roughly with the cube of speed, so halving the speed uses about an eighth of the energy. Running twice as long at half speed is dramatically cheaper for the same turnover.
The formula
GPM = gallons / turnover hours / 60
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