Turnover
Also called: turnover rate, turnover time, one turnover a day.
Turnover is the time it takes a pool's pump and filter to move a volume of water equal to the whole pool. Residential codes use turnover to size equipment: a pump and filter able to turn the pool over in 12 hours or less. Turnover is a sizing rule, not a daily quota.
Why it matters
The codes use turnover in two directions. The floor: the Florida Building Code and the ICC pool code require equipment able to turn the pool over in 12 hours or less, so your gallons ÷ 720 is the minimum GPM your equipment must be able to deliver. The ceiling: the energy codes cap everyday filtration flow at a 6-hour turnover or 36 GPM, whichever is greater, so gallons ÷ 360 is the most your filtering speed should move. Neither says how many hours a day to run; only public pools carry a daily operating turnover rule. Your hours come from skimming, mixing chlorine and, on salt, running the cell.
In numbers
For a 20,000-gallon pool the code band is about 28 to 56 GPM.