PoolOwl

Equipment & energy

Pool Pump Run Time Calculator

Work out how many hours your pump needs each day to filter all your water, from your pool size and flow rate.

What you'll need (2)
  • Your pool's volume in gallons
  • Your flow rate in gallons per minute (GPM)
Units
Your pool
Don't know it? Work it out in about a minute.
Your pump

Flow rate is the hardest number to know. A flow meter on the return line is best; otherwise use your pump's curve and your system's resistance, or a variable-speed pump's display.

Gallons per minute through the filter. Example: 40.
Turnovers per day

Your result

Calculated

Your result will appear here

Enter your pool size and pump flow rate.

Turnover, simply

A turnover is the time it takes the pump to move a volume equal to the whole pool through the filter:

turnover hours = gallons ÷ (gallons per minute × 60)

A 20,000-gallon pool with 40 GPM of flow turns over in about 8.3 hours.

One turnover doesn’t mean every drop gets filtered once. Filtered water mixes back in, so some passes through twice while some is missed. In practice, about one turnover a day keeps most residential pools clear when the chemistry is right. Heavily used pools, or ones fighting algae, benefit from more.

Use the number as a starting point

The calculator gives hours for the turnovers you pick. Then adjust based on what you see:

  • Clear water and steady chlorine? Try trimming runtime in small steps.
  • Cloudy water, or chlorine dropping faster than usual? Run longer and check the filter.

Variable-speed pumps

With a variable-speed pump, run it longer at a lower speed. Flow drops in proportion to speed, but power drops much faster, roughly with the cube of speed. At half speed you need twice the hours to move the same water but use far less electricity. The pump energy cost calculator compares the two.

Some equipment needs a minimum flow: heaters, salt cells and pressure-side cleaners. Check those manuals before setting very low speeds.

Assumptions and limitations

  • Turnover is a planning figure. Filtered water mixes back into the pool, so one turnover doesn't mean every gallon passed through the filter exactly once.
  • Accuracy depends on your flow rate, which falls as the filter loads up and changes with pump speed.

Key terms

Common questions

Do I need to run my pool pump 24 hours a day?

Rarely. ENERGY STAR notes that running a filter 6 hours a day instead of 24 cuts its energy use by 75%. Most residential pools stay clear on roughly one turnover a day, as long as chlorine is maintained.

Is it better to run the pump during the day or at night?

Daytime running keeps chlorine mixed when sunlight and swimmers use it fastest. Night running can be cheaper on time-of-use electricity plans. Many owners split the difference.

How do I find my flow rate?

The most reliable way is an inline flow meter on the return pipe. Variable-speed pumps often display an estimated flow. Otherwise, a pump's performance curve plus your system's pressure gives an estimate, and a pool professional can help with that.

Sources and methodology references

  1. ENERGY STAR: Pool pumps, US EPA ENERGY STARReduced filtration time and variable-speed savings.

Published October 2, 2026. Results are calculated directly from your inputs. See how our calculators work.

Spotted a wrong result or an outdated source? Report a problem with this calculator.

Related tools