Turn your pool over in 8 hours.

That’s the rule of thumb: your pump should cycle all the water through the filter in roughly 8 hours. To get the flow rate, divide your pool volume (in gallons) by 480 (8 hours × 60 minutes). For a typical 20,000-gallon pool that’s about 42 GPM.

But don’t just buy the biggest pump. Your filter has a maximum flow rate — exceeding it damages the filter or wastes energy. Check the filter’s spec sheet. Also, plumbing