Enter your pool's gallons, how many hours one turnover should take and the kind of filter. You get the flow that turns the water over in that time, the smallest Pentair filter rated for it, and the pipe sizes the energy standard asks for.
Your pool needs
42 gpm turns 20,000 gallons over in 8 hoursPentair Clean & Clear Plus CCP320 (cartridge, 120 gpm) · pipes 2 in. suction, 2 in. return at 56 gpm
Quick answer: divide the gallons by the turnover time in minutes. A 20,000-gallon pool turned over in 8 hours needs 42 gpm (20,000 ÷ 480). Pentair’s smallest Clean & Clear Plus cartridge, the CCP320, is rated 120 gpm. The energy standard ANSI/APSP/ICC-15 sizes a home pool’s pipes at a 6-hour turnover or 36 gpm, whichever is greater: 56 gpm here, through 2 in. pipes.
How to use the pool pump and filter size calculator
- Enter the gallons. Not sure? The pool volume calculator works them out from the size and depth.
- Pick the hours for one turnover: 6, 8, 10 or 12, the times Pentair’s filter tables and the energy standard use.
- Pick the filter: cartridge, D.E. or sand.
- Know your pump’s flow? Enter it to see how many hours one turnover takes.
You get the flow in gallons a minute, the smallest filter in Pentair’s range rated for it, the energy standard’s filtration rate and the pipe sizes that keep the water under the code’s speed limits. The chart puts your flow beside each filter’s rating.
The rules, and where they come from
Turnover. One turnover is the whole pool going through the filter once. Flow (gpm) = gallons ÷ (hours × 60). Pentair prints every filter’s “Turnover Capacity” the same way: its flow × 60 × 8, 10 or 12 hours.
Filters. From Pentair’s 2025–2026 catalog. Clean & Clear Plus cartridges are rated at “Residential rate .375 GPM per sq. ft. of filter area”. FNS Plus D.E. filters take 2 gpm a square foot, and Triton II sand filters are rated from 63 to 106 gpm.
Pump and pipes. ICC’s notes on the 2021 International Swimming Pool and Spa Code: ANSI/APSP/ICC-15 sizes a home pool’s filtration “6-hour turnover rate, or 36 gpm, whichever is greater”, “Pool gallons ÷ 360 minutes = filtration flow rate”. Its pipes keep the water under “6 feet per second … in the suction piping” and 8 in the return. California’s energy code says the filtration flow “may not be greater than the rate needed to turn over the pool water volume in 6 hours or 36 gallon per minute (gpm), whichever is greater”.
Flow by pool size and turnover time
| Pool | 6 hours | 8 hours | 10 hours | 12 hours | Pipes (suction / return) |
|---|---|---|---|---|---|
| 10,000 gal | 28 gpm | 21 gpm | 17 gpm | 14 gpm | 1.5 in. / 1.5 in. |
| 15,000 gal | 42 gpm | 31 gpm | 25 gpm | 21 gpm | 2 in. / 1.5 in. |
| 20,000 gal | 56 gpm | 42 gpm | 33 gpm | 28 gpm | 2 in. / 2 in. |
| 25,000 gal | 69 gpm | 52 gpm | 42 gpm | 35 gpm | 2.5 in. / 2 in. |
| 30,000 gal | 83 gpm | 63 gpm | 50 gpm | 42 gpm | 2.5 in. / 2 in. |
| 40,000 gal | 111 gpm | 83 gpm | 67 gpm | 56 gpm | 3 in. / 2.5 in. |
Pipes are Schedule 40 PVC sized at the energy standard’s rate (6-hour turnover, 36 gpm at least): the suction line at 6 ft/s and the return at 8, from ICC’s table (2 in. carries 63 gpm at 6 ft/s and 84 at 8).
Pentair’s filters and what they turn over
| Filter | Area | Rated flow | Gallons in 8 hours |
|---|---|---|---|
| Clean & Clear Plus CCP320 (cartridge) | 320 sq ft | 120 gpm | 57,600 |
| Clean & Clear Plus CCP420 (cartridge) | 420 sq ft | 150 gpm | 72,000 |
| FNS Plus FNSP36 (D.E.) | 36 sq ft | 72 gpm | 34,560 |
| FNS Plus FNSP48 (D.E.) | 48 sq ft | 96 gpm | 46,080 |
| FNS Plus FNSP60 (D.E.) | 60 sq ft | 120 gpm | 57,600 |
| Triton II TR 60 (sand) | 3.14 sq ft | 63 gpm | 30,240 |
| Triton II TR 100 (sand) | 4.91 sq ft | 74 gpm | 35,520 |
| Triton II TR 140 (sand) | 7.06 sq ft | 106 gpm | 50,880 |
From Pentair’s 2025–2026 pool product catalog. “Actual system flow will depend on plumbing”, so these ratings are the most each filter should see, not what a pump will push through it.
Worked examples
42 gpm turns 20,000 gallons over in 8 hours: the CCP320 cartridge is rated 120 gpm. The energy standard sizes the pipes at 56 gpm: 2 in. suction and return.
28 gpm turns 13,594 gallons over in 8 hours: a 24 ft round pool with 4 ft of water. The Triton II TR 60 is rated 63 gpm, and 1.5 in. pipes carry the standard’s 38 gpm.
92 gpm turns 33,000 gallons over in 6 hours: Pentair’s 40 × 20 ft example pool. The TR 140 sand filter is rated 106 gpm; the suction line goes to 3 in.
63 gpm turns 30,000 gallons over in 8 hours: the FNSP36 D.E. filter is rated 72 gpm. At the standard’s 83 gpm, pick the FNSP48 or run the pump slower.
Common mistakes
- Buying by horsepower. A pump’s flow depends on the head it pumps against: its pipes, its filter and its height. Pick a pump whose curve gives your flow at your head.
- A filter smaller than the pump. Pentair rates each filter by the most flow it should see. Keep the pump’s flow at or under that rating, or pick the next filter up.
- Pipes too small for the pump. 1.5 in. pipe carries 38 gpm at the 6 ft/s suction limit. ICC’s notes: over-pumping and under-piping make “high pressure, excessive noise, vibration”.
- Using the wall height for the gallons. Measure the water, not the wall, or the flow comes out too high.
More on pools at Dreamy Home Style
Keeping the water clean too? The pool salt and chlorine calculator and the pool water balance calculator take the same gallons. Planning the equipment pad and the yard? Draw them to scale in the free 2D floor planner.
Pool pump and filter questions
What size pool pump do I need?
One that gives your turnover flow at your plumbing’s head: the gallons ÷ (the hours × 60). A 20,000-gallon pool needs 42 gpm for an 8-hour turnover. The energy standard sizes home pool filtration at a 6-hour turnover or 36 gpm, whichever is greater.
How do I use a pool pump size calculator?
Enter the gallons and the turnover time. It divides one by the other in minutes to give the gallons a minute, then the filter and pipe sizes for that flow.
What size pool filter do I need?
One rated for at least your turnover flow. Pentair prints each filter’s turnover at 8, 10 and 12 hours: its CCP320 cartridge turns over 57,600 gallons in 8 hours, its Triton II TR 60 sand filter 30,240.
What is a pool’s turnover rate?
The time it takes the whole pool to pass through the filter once. Pentair’s filter tables use 8, 10 and 12 hours; the energy standard ANSI/APSP/ICC-15 uses 6 hours for sizing the pipes.
How many gallons a minute should my pool pump run?
Gallons ÷ (hours × 60). 15,000 gallons in 8 hours is 31 gpm; 30,000 gallons is 63 gpm.
How long should I run my pool pump?
Long enough for one turnover: the gallons ÷ (the pump’s flow × 60). A 20,000-gallon pool on a 42 gpm pump turns over in 7.9 hours. Enter your pump’s flow above to get yours.
Can a pool filter be too big?
Pentair rates its filters by the most flow they should see, so a bigger filter at the same flow simply runs below its rating. The size to watch is the smallest: its rating must be at or above your pump’s flow.