Pool Pump Runtime Calculator
Pump hours for one and two pool turnovers.
What it does
Turnover time is how long the pump needs to push one pool volume through the filter. It sets the daily schedule and the power bill. A 15,000 gal pool at 40 GPM turns in 6.25 h, so one pass a day means about six and a quarter run hours.
The tool above shows one turnover, two turnovers, and hourly flow. Defaults give 6.25 h per turnover and 12.5 h for two at 2,400 gal per hour. The metric mirror at 57,000 L and 150 LPM gives 6.33 h and 12.67 h at 9,000 L per hour. Home pools often target one pass daily, while public spas and wading pools must turn far faster by code.
Flow accuracy matters more than volume accuracy. Pumps publish max flows without pipes, filters, heaters, or valves, while the pool sees working flow at head. A flow meter or the pump curve at measured head gives the honest number; nameplate numbers understate hours and leave water dull.
This page times water movement only. It does not test chemistry, fix algae, or size pipes and filters. Clear water needs turnover plus balanced chlorine, pH, and brushing.
How to use
- Pick imperial (gal, GPM) or metric (L, LPM).
- Enter the pool water volume.
- Enter the metered flow through the filter.
- Read one turnover first, then two.
- Plan daily run time for the turnovers wanted.
- Re‐check after filter cleans or valve changes shift flow.
Formula
- volume
- Pool water volume in gal or L.
- flow
- Metered flow through the filter in GPM or LPM.
- turnovers
- Count of full volume passes per day, often one at home.
Flow is measured through the filter at system head, in GPM or LPM. At zero flow there is no turnover; variable speed math assumes flow follows speed, subject to heater and feeder minimums.
Worked example
Example: 15,000 gal at 40 GPM
Defaults: imperial 15,000 gal with 40 GPM through the filter. Metric mirror is 57,000 L at 150 LPM.
- Inputs (imperial default): 15,000 gal pool, 40 GPM flow.
- Hourly flow: 40 times 60 is 2,400 gal per hour.
- One turnover: 15,000 / 2,400 is 6.25 h per turnover.
- Two turnovers: 6.25 times 2 is 12.5 h for two.
- Metric mirror (57,000 L at 150 LPM) gives 6.33 h and 12.67 h. Tool shows the same.
Reference table
| Pool and flow | One turnover | Two turnovers |
|---|---|---|
| 15,000 gal at 40 GPM | 6.25 h | 12.5 h |
| 20,000 gal at 50 GPM | 6.67 h | 13.33 h |
| 10,000 gal at 25 GPM | 6.67 h | 13.33 h |
| 57,000 L at 150 LPM | 6.33 h | 12.67 h |
| 40,000 L at 200 LPM | 3.33 h | 6.67 h |
Limits
- Movement only. Chemistry and brushing excluded.
- Working flow assumed. Nameplate max misleads.
- Single pump path. Features on separate pumps excluded.
- No code design. Public venues follow local rules.
Common mistakes
- Entering pump max instead of metered filter flow.
- Assuming one turnover filters every gallon once.
- Running too little after storms or heavy use.
- Ignoring heater minimums on low variable speeds.
- Sizing time from volume guesses instead of metered flow.
Try it yourself
Quick checks. Answers sit tucked under each question.
20,000 gal at 50 GPM?
Hourly is 50 times 60 is 3,000 gal per hour. One is 20,000 / 3,000 is 6.67 h. Two is 13.33 h.
40,000 L at 200 LPM?
Hourly is 200 times 60 is 12,000 L per hour. One is 40,000 / 12,000 is 3.33 h. Two is 6.67 h.
Questions
How is turnover time figured?
Hours = gallons / (GPM times 60). Here 15,000 / 2,400 is 6.25 h per turnover.
How long for two turnovers?
Twice one turnover. Here 12.5 h for two passes.
Which flow number do I enter?
Use metered flow through the filter at working head. Nameplate max overstates real flow through pipes and a dirty filter.
How many turnovers a day?
Many homes aim for one pass a day. Public venues follow stricter code maxima by pool type.
Does low speed save power?
Flow scales with speed on variable pumps, so half speed over double time moves the same water for less power. Check minimum flows for heaters and feeders.
Does one turnover mean clean water?
No. One pass does not mean every gallon saw the filter once. Mixing is imperfect, so clarity needs time plus chemistry.