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Turnover rate math

Reviewed by the Pool Operator Prep editorial team. Formula verified against public pool-hydraulics references: 2026-07-24.

How do you calculate a pool's turnover rate?

Divide the pool volume in gallons by the flow rate in gallons per minute to get the turnover time in minutes, then divide by 60 for hours. A 90,000 gallon pool moving 300 gallons per minute turns over in 300 minutes, which is 5 hours.

Turnover tells you how long the pump takes to filter a volume of water equal to the whole pool, and health codes set a limit on it. Below is the formula, a worked example, the wrong-unit slip that costs easy points, and eight randomized problems. See how volume feeds this on the pool volume page.

Formula · worked example
Turnover (min) = volume (gal) ÷ flow (gpm)   →   ÷ 60 for hours
Worked example
Pool: 120,000 gal, flow 250 gpmMinutes: 120,000 ÷ 250 = 480 minTo hours: 480 ÷ 60
= 8.0 hour turnover

The error class that fails people · Answering in the wrong unit The division gives minutes. If the question asks for hours you must divide by 60, and if it asks for minutes you must not. A correct 480 becomes a wrong answer the moment it is labeled 480 hours instead of 8 hours. Read the unit the question wants before you circle anything.

Schematic of a pool's circulation loop: water leaves the pool, passes through a filter and pump, and returns, with a large coral arrow tracing one full turnover of the whole pool volume past a clock.
One turnover is the time to circulate the entire pool volume through the filter once (the coral loop).

Drill it: 8 randomized problems

Eight turnover problems mixing minutes-and-hours conversions plus one code-compliance judgment. Answer to see the full worked solution, with wrong choices built from the wrong-unit slip so a miss pinpoints the error. Free and ungated, progress stays on your device.

Sample problems

A preview of the kind of problem in the set, authored from the underlying pool-hydraulics facts. Open the answer for the full worked solution.

  1. A 66,000 gallon pool has a flow rate of 200 gpm. What is its turnover time in hours?

    • A 330 hours
    • B 2.8 hours
    • C 5.5 hours
    • D 11.0 hours
    Show the worked solution

    Correct answer: C. 5.5 hours

    Turnover in minutes = volume / flow = 66,000 / 200 = 330 minutes. Convert to hours by dividing by 60: 330 / 60 = 5.5 hours. Answer 330 is the right number left in minutes, the single most common turnover error.

  2. A 120,000 gallon pool circulates at 250 gpm. What is the turnover time in hours?

    • A 8.0 hours
    • B 480 hours
    • C 0.1 hours
    • D 480.0 hours
    Show the worked solution

    Correct answer: A. 8.0 hours

    120,000 / 250 = 480 minutes, then 480 / 60 = 8.0 hours. Leaving it at 480 reports minutes as if they were hours.

Questions people ask

What is a good turnover rate for a pool?

Public-pool health codes commonly require the whole volume to circulate in six hours or less, and many spas and wading pools require much faster turnovers. A shorter turnover time is better because the water passes through the filter more often. Check the code that applies to your pool for the exact requirement.

Is turnover measured in minutes or hours?

The raw calculation, volume divided by flow rate in gallons per minute, gives minutes. Codes and exam questions usually ask for hours, so you divide the minutes by 60. The mistake that fails people is reporting the minutes figure as though it were hours, so always match the unit the question asks for.

What is the difference between turnover rate and flow rate?

Turnover rate is the time to circulate one full pool volume through the filter. Flow rate is the gallons per minute the pump moves. They are linked: turnover equals volume divided by flow, and if you know the turnover you need, you can solve for the flow rate the pump must deliver.

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