What one turnover means
One turnover means a volume approximately equal to the pool’s capacity has passed through the filter. It does not mean every drop has been filtered.
Calculators
Filtration
Pool pump flow calculator
Enter pool volume and target turnover time. Estimate the required flow and the operating time of an existing pump.
Calculator
Estimate required pump flow
Enter pool volume, target turnover time and an assumed system flow reduction. Rated flow is often higher than actual flow through a filter, hoses and pipework. Verify any selection with the pump curve.
Key terms
How to read the flow calculation
Actual flow is lower than maximum flow
Catalogue flow is often quoted under favourable conditions. Connecting pipes, valves and a filter reduces it.
Allow for system resistance
Filters, hoses, valves, relevant elevation differences and dirt increase the resistance the pump works against.
Operating time
Sometimes the solution is a longer or better-timed daily schedule, not a larger pump.
Common mistakes
Mistakes that lead to the wrong pump
Do not choose by the largest catalogue number. Consider volume, filtration, pipework and how the system will actually operate.
- 1calculating only from motor power in watts
- 2ignoring reduced flow through the filter
- 3running filtration for too little time during hot weather
- 4comparing pumps without knowing pool volume
- 5buying a pump without checking filter compatibility
- 6blaming chemicals when circulation is insufficient
Next steps
Check the result against the rest of the system
Pool pumps
Learn how to match the pump with the filter, pipes and other components.
Learn morePool volume
If volume is unknown, calculate how much water the pump needs to circulate first.
Learn moreCloudy water
If the pump runs but water stays cloudy, check flow, filtration and water chemistry.
Learn moreFAQ
Pump sizing questions answered
How quickly should the pump turn the water over?
A turnover over several hours can be a starting design assumption for a domestic pool. The actual schedule depends on volume, use, temperature, filtration and applicable requirements.
Should I compare watts or m³/h?
For filtration, flow in m³/h and compatibility with the filter are more useful. Motor power alone does not show how a pump will perform in your installation.
Why does the calculator include system losses?
Because actual flow is usually lower once water passes through the filter, hoses and pipework. The percentage is an assumption for comparison, not a substitute for a pump-curve calculation.
Are two turnovers a day always enough?
No single number suits every pool. Two theoretical turnovers may be a useful starting estimate, but heat, heavy use or water problems can require longer filtration. Water quality and equipment requirements still need checking.