Turnover and Pump Runtime

Excel Formulas › Pool & Spa Service

All versions

A pool should circulate its full volume (a turnover) regularly. Volume ÷ flow rate gives the hours for one turnover — the basis for daily pump runtime.

Quick formula: hours for one turnover:
=gallons / flow_rate_gpm / 60
Volume over flow rate (GPM) over 60 gives turnover hours. 20,000 gal at 50 GPM is ~6.7 hours.

The example

20,000 gal, 50 GPM.

AB
1ItemValue
220000 / 50 / 60—
3Turnover→ ~6.7 hrs

The formula

The formula:

=gallons / flow_rate_gpm / 60 // volume ÷ GPM ÷ 60

How it works

How it works:

  1. One turnover = volume ÷ flow rate (GPM) ÷ 60 (minutes to hours).
  2. Most pools target 1–2 turnovers per day — multiply for runtime.
  3. A variable-speed pump trades flow for energy — lower GPM, longer runtime, less cost.
  4. Confirm the real flow rate with a flow meter; rated GPM overstates actual.

Educational use only — not chemical-safety or professional advice. Pool chemical dosing varies by product strength, water chemistry, and local rules. Always follow the product label, add chemicals to water (never water to chemical), test before and after, and never mix chemicals. Verify with a professional.

Try it: interactive demo

Live demo

Gallons, flow rate (GPM), turnovers/day.

Per turnover · Runtime

Variations

Daily runtime

× turnovers:

=turnover_hours * turnovers_per_day

Required GPM

For a target turnover:

=gallons / (target_hours * 60)

Turnovers in a runtime

How many:

=runtime_hours / turnover_hours

Pitfalls & errors

÷ 60. GPM is per minute — divide to get hours.

Real flow. Use measured GPM, not the pump’s rated max.

1–2/day. Adjust turnovers to bather load and season.

Practice workbook

📊
Download the free Turnover and Pump Runtime practice workbook
A turnover sheet with the daily-runtime, required-GPM, and count variants, plus 4 challenges with answers. No sign-up required.

Frequently asked questions

How do I calculate pool turnover time in Excel?
Volume over GPM over 60: =gallons / flow_rate_gpm / 60. 20,000 gal at 50 GPM is ~6.7 hours.
How much should the pump run daily?
Multiply turnover hours by turnovers per day (usually 1–2): =turnover_hours * turnovers_per_day.
What GPM do I need for a target turnover?
=gallons / (target_hours * 60).

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Related formulas: Flow rate (GPM) · Pool volume in gallons · Pool heating cost