Pool Turnover Rate & Pump GPM Calculator
The flow rate (gpm) your pool pump must deliver for a target turnover time, your actual turnover from a flow meter reading, and whether your filter is big enough for that flow.
Formula
Required flow (gpm) = gallons ÷ (turnover hours × 60). Actual turnover (hours) = gallons ÷ (measured gpm × 60). Filter max flow = filter area × rated gpm per sq ft.
Worked example
Inputs: Pool volume = 36000 gal; Target turnover time = 6 hours; Flow meter reading (0 to skip) = 60 gpm; Filter area (from the filter label, 0 to skip) = 0 sq ft; Max filter rate (from the filter label) = 0 gpm/sq ft.
| Required flow gpm | 100 |
|---|---|
| Gallons per hour | 6,000 |
| Actual turnover hours | 10 |
| Turnovers per 24h at measured flow | 2.4 |
| Meets target | No |
| Filter max flow gpm | — |
| Filter ok for required flow | — |
Turnover = the time to pass the whole pool volume through the filter once. Required public-pool turnover depends on your state (e.g., 6 h in New York, 8 h for swimming pools in Maryland, 30 min for spas). Residential pools follow the pump and filter maker's guidance.
FAQ
How do I calculate pool turnover?
Divide pool gallons by the flow meter reading times 60. A 36,000 gallon pool at 60 gpm turns over in 36,000 ÷ 3,600 = 10 hours. To reach 6 hours it needs 36,000 ÷ 360 = 100 gpm (the Virginia health department's worked example).
What turnover rate is required?
It depends on the state and pool type. New York requires public pools to turn over in 6 hours. Maryland requires swimming and diving pools to turn over in 8 hours, recreation and therapy pools in 6, wading pools in 2 and spas in 30 minutes. The Virginia guide recommends 8 to 12 hours for semi-public pools.
What about my backyard pool?
Residential pools are not covered by those public-pool rules. Follow your pool builder's design flow and your pump and filter maker's guidance.
Why check the filter?
A filter is rated for a maximum flow per square foot. If the pump pushes more, the filter works poorly. Enter the area and rate from the filter label to check it against the flow you need.
How many turnovers a day do I get?
24 ÷ turnover hours. At a 10 hour turnover the water passes through the filter 2.4 times a day if the pump runs 24 hours.
Sources
- Virginia Department of Health (Portsmouth), Pool Operation and Maintenance Guide: turnover hours = gallons ÷ (gpm × 60); flow rate = gallons ÷ (turnover hours × 60); recommended public 6 h, semi-public 8–12 h, wading 2 h, spa 30 min
- New York State Sanitary Code 10 NYCRR 6-1.11(a): the entire pool volume must be recirculated and treated in six hours
- Maryland COMAR 10.17.01.25 B, minimum turnover rates: swimming and diving pools gallons ÷ 480 min, recreation/therapy ÷ 360, wading ÷ 120, spas ÷ 30 (via Cornell LII)
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Last reviewed 2026-10-30.