Pool Turnover Rate Formula
The Formula
| Symbol | Description | Unit |
|---|---|---|
Volume | Total pool volume in gallons | gallons |
GPH | Pump flow rate in gallons per hour (GPM × 60) | gallons/hour |
Turnover Time | Time in hours to circulate the full pool volume once through the filter | hours |
Worked Example
Pool: 18,000 gallons. Pump flow rate: 60 GPM.
- GPH = 60 × 60 = 3,600
- Turnover time = 18,000 ÷ 3,600 = 5 hours
This pump turns over the pool every 5 hours, meeting the 8-hour recommendation.
Now calculate required pump run time for one daily turnover: - Run time for one turnover = 18,000 ÷ 3,600 = 5 hours per day minimum.
How This Formula Works
Turnover rate is the time required for the pump to move the entire pool's volume through the filter once. Shorter turnover times mean more effective filtration, but require a larger pump or longer run times.
- PHTA recommends residential pools turn over at least once every 8 hours.
- Commercial pools and health department regulations often require 6-hour or even 4-hour turnovers.
- GPM (gallons per minute) × 60 = GPH (gallons per hour).
- A pump rated at 60 GPM operates at 3,600 GPH.
- To find required run time at a specific flow rate: Required Hours = Volume ÷ GPH.
Limitations & Notes
Published GPM ratings for pumps are typically at zero head pressure. Actual flow rate in a plumbed system is lower due to resistance from pipes, fittings, valves, and the filter. Always use the pump's curve at your system's head pressure for accurate calculations.
Last reviewed: 2026-06-01