How to use this calculator
- Get the volume. Length × width × average depth for rectangles; sum sections for freeform shapes.
- Set the turnover target. 6–8 h residential practice; the health code governs public pools and spas.
- Read required flow. That is delivered flow — check the pump curve at the real system head.
- Check filter and pipe limits. Filter flux rating and suction/return velocity caps must both clear the chosen flow.
How it works
Turnover is one division — volume over time — but each side of it hides real engineering: the volume is fixed, while the flow must survive the filter, heater and plumbing losses between the pump and the water:
Q_req = V / t · t_actual = V / Q_pump · turnovers/day = 24 / t
The head side of that story is the pipe flow pressure drop calculator, suction-side safety is the pump NPSH calculator, and pipe sizing against velocity limits is the pipe size by flow calculator.
Worked example
Verified against the live calculator
A 60,000 L (15,850 gal) pool, 8-hour
target, existing pump delivering 150 L/min (40 gpm):
Q_req = 60,000 / (8 × 60) = 125 L/min (33 gpm) · actual = 60,000 / (150 × 60) = 6.7 h · 3 turnovers/day
The pump clears the target with margin — 6.7 hours against 8 — and
the system filters 180,000 L per day at the required
flow. If that same pump only delivers 100 L/min once the filter
loads up, the turnover stretches to 10 hours: delivered flow, not
nameplate flow, is the number that matters.
Frequently asked questions
How do you calculate pool turnover rate?
Pump flow = pool volume ÷ turnover time. A 60,000 L (15,850 gal) pool on an 8-hour turnover needs 125 L/min — about 33 gpm of DELIVERED flow at the system head, not the pump's open-flow rating.
What is a good turnover time for a pool?
6–8 hours is common residential practice; public and commercial pools take a required turnover from the local health code (often 6 hours or faster), and spas turn over in well under an hour. The number is a target you enter, not a constant this tool assumes.
How do I check the pump I already have?
Enter its delivered flow and read the actual turnover: a 150 L/min (40 gpm) pump turns the example pool in 6.7 hours — comfortably inside an 8-hour target. Delivered flow means the pump curve at the real head with a dirty-ish filter, which is well below the box rating.
Is a bigger pool pump always better?
No — filters have flux limits (flow per square foot of media) and plumbing has velocity limits, and pushing past either churns water without cleaning it. Variable-speed pumps usually win by running longer at lower flow: same daily filtered volume, much less power, since pump power rises roughly with the cube of speed.
Method & assumptions
- Circulation arithmetic only — the turnover requirement itself comes from practice (6–8 h residential) or the local health code (public pools, spas), entered by you.
- Flow means delivered flow at the actual system head; pump curves, filter condition and plumbing losses set it, not the box label.
- Filter flux ratings and pipe velocity limits cap usable flow independently — check both at the chosen rate.
- Chemical balance, sanitizer feed and bather-load surcharges are water-treatment territory beyond this screen.