Best for
- Variable-speed pump owners
- Owners trying to reduce electricity use
- Pools with known or estimated flow rate
Watch for
- Filter pressure and plumbing resistance reduce real flow
- Salt systems and heaters may require minimum flow/runtime
- Turnover alone does not guarantee water quality
The core turnover formula
Runtime hours = pool gallons × desired turnovers ÷ flow rate in GPM ÷ 60. A 20,000-gallon pool at 50 GPM needs about 6.7 hours for one theoretical turnover.
Why variable speed changes the answer
Lower pump speeds often move less water per hour but can use dramatically less power. The cheapest schedule can therefore be a longer runtime at a lower speed, provided skimming, chlorination and equipment minimum-flow requirements are met.
Use the calculator as a planning baseline
Start with estimated flow and one turnover, then adjust based on sanitizer production, debris, weather and clarity. If you do not know actual GPM, treat the result as a planning estimate rather than a precise hydraulic measurement.
Pool-equipment claims are often based on different pool sizes, operating modes or test conditions. Compare the same job, pool dimensions and ownership assumptions before choosing a product.