What size pump for a 15,000 gallon pool?
A 15,000 gallon pool needs a pump that moves about 31.3 gallons per minute to turn the water over in 8 hours, which is 1,875 gallons an hour.
How to work it out
- 15,000 gal ÷ (8 h × 60 min) = 31.3 gpm
- Slowest: 15,000 gal ÷ 1,440 min = 10.4 gpm (39 L/min)
- Fastest: the larger of 15,000 gal ÷ 360 min and 36 gpm = 41.7 gpm (158 L/min)
- Filter: rated for at least the pump’s 31.3 gpm (118 L/min); DOE’s efficiency advice adds 50%: 46.9 gpm (177 L/min). Sand bed 31.3 gpm ÷ 20 gpm per sq ft = 1.56 sq ft
Fifteen thousand gallons covers a lot of pools: a 15 × 30 sport pool, a kidney or freeform of 400-odd square feet, or a large above-ground oval. At this size the flow is modest enough that pipe size rarely limits you, and the choice is mostly about how long you want the pump to run.
Adjust for your project
- Water moved per hour
- 1,875 gal
- Slowest allowed (one turnover in 24 hours)
- 10.4 gpm (39 L/min)
- Design limit where adopted (6-hour turnover or 36 gpm)
- 41.7 gpm (158 L/min)
- Pipe check
- OK: 1-1/2 in pipe carries up to 45 gpm
- Filter rated for at least (your pump’s flow)
- 31.3 gpm (118 L/min)
- DOE efficiency advice (not a minimum): rated 50% above
- 46.9 gpm (177 L/min)
- Sand filter area at 20 gpm per sq ft
- 1.56 sq ft
- Smallest listed sand filters that meet it
- Hayward S180T (35 gpm) or Pentair Triton II TR40 (38 gpm)
- Horsepower alone tells you little. DOE says a pump of 0.75 hp or smaller is generally enough for a home pool; a variable-speed pump lets you run the flow above for longer at low speed. See what a pump costs to run.
15,000 gallon pool by turnover time
| Turnover | Pump flow you need | Filter rated for at least (your pump’s flow) | Sand filter area at 20 gpm per sq ft |
|---|---|---|---|
| 6 hours | 41.7 gpm (158 L/min) | 41.7 gpm (158 L/min) | 2.08 sq ft |
| 8 hours | 31.3 gpm (118 L/min) | 31.3 gpm (118 L/min) | 1.56 sq ft |
| 10 hours | 25 gpm (95 L/min) | 25 gpm (95 L/min) | 1.25 sq ft |
| 12 hours | 20.8 gpm (79 L/min) | 20.8 gpm (79 L/min) | 1.04 sq ft |
| 24 hours | 10.4 gpm (39 L/min) | 10.4 gpm (39 L/min) | 0.52 sq ft |
What 31 gpm means in practice
At 31 gpm, 1-1/2 inch pipe (rated to 45 gpm in Hayward’s table) has plenty of headroom, and even 1-1/4 inch pipe at 30 gpm is only just over its line. That headroom is useful: you can shorten the turnover to 6 hours (about 41.7 gpm) after a storm or a pool party, then drop back for normal days.
- Minimum. One turnover a day is about 10.4 gpm. A variable-speed pump can sit near that overnight and still meet DOE Building America’s once-a-day floor.
- Filter. It needs a rating of at least the 31 gpm flow; DOE’s efficiency advice adds 50% (about 47 gpm), which points to a Pentair TR50 (49 gpm) or Hayward S220T (52 gpm) among the filters listed here.
- Bed area. At 20 gpm per sq ft, 31 gpm needs at least 1.56 sq ft of sand bed before any margin.
- Above-ground version. If your 15,000 gallons is an above-ground pool, check the size of the pump’s hose ports and use that row of the pipe check.
If the pool is larger, what size pump for a 20,000 gallon pool shows where 1-1/2 inch pipe starts to pinch; a 24 ft round sits a little lower, on what size pump for a 24 ft above-ground pool. For daily chemistry at this volume, see how much chlorine for a 15,000 gallon pool.
Different size? Use the full Pool Pump Size Calculator (GPM & Turnover).
What you’ll need
- Variable-speed pool pumpPremium price
Runs slower for longer and uses far less electricity for the same turnover. Check it suits your pipe size and filter.
See options on Amazon (opens in a new tab) - Sand filter (top-mount)Premium price
Simple and durable. Size by flow: the filter’s rated maximum should be at or above your pump’s flow.
See options on Amazon (opens in a new tab) - Pool filter sand (#20 silica, 50 lb)Budget price
The grade most sand filters are designed for (about 0.45–0.55 mm). Check your filter’s label for the exact amount.
See options on Amazon (opens in a new tab)
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Frequently asked questions
What gpm for a 15,000 gallon pool on a 10-hour turnover?
About 25 gpm (95 L/min). The smallest listed sand filters for that flow: Hayward S144T (25 gpm) or Pentair Triton II TR40 (38 gpm).
Is 1-1/4 inch pipe big enough for a 15,000 gallon pool?
Only just not. On an 8-hour turnover the flow is 31.3 gpm (118 L/min), and the pipe check reads: Too much for 1-1/4 in pipe (max 30 gpm): use bigger pipe or a longer turnover. A 9-hour turnover brings the flow under 30 gpm.
Other common sizes
- What size pump for a 20,000 gallon pool — 41.7 gpm (158 L/min)
- What size pump and sand filter for a 24 ft above-ground pool — 27.1 gpm (103 L/min)
Sources
- US DOE Building America — Measure guideline: replacing single-speed pool pumps with variable-speed pumps (Hunt & Easley, 2012) (opens in a new tab) — A turnover every 24 hours is the minimum (volume ÷ 1,440 gpm); APSP suggests a pump capable of two turnovers a day; maximum filtration flow = a 6-hour turnover or 36 gpm, whichever is greater (California Energy Commission, adopted in ANSI/APSP/ICC-15).
- US DOE Energy Saver — Choosing, installing and operating an efficient swimming pool pump (archived) (opens in a new tab) — Use the smallest pump possible; 0.75 hp or smaller is generally sufficient for residential pools; choose a filter rated at least 50% above the pool’s design flow; lower hydraulic resistance cuts pump electricity by up to 40%.
- Hayward ProSeries high-rate sand filter manual (IS210TS Rev A) (opens in a new tab) — Maximum recommended system flow by pipe size: 1 in 20 gpm, 1-1/4 in 30, 1-1/2 in 45, 2 in 80, 2-1/2 in 110, 3 in 160.
- Hayward ProSeries sand filter brochure (2011) (opens in a new tab) — Design flows based on 20 gpm per sq ft: S180T 35, S210T 44, S220T 52, S244T 62, S270T 74 gpm.
- Hayward ProSeries above-ground sand filter sell sheet (2025) (opens in a new tab) — S144T 25, S166T 30, S180T 35, S210T 44, S230T 54 gpm.
- Pentair Triton II sand filter brochure (opens in a new tab) — TR40 38 gpm, TR50 49 gpm, TR60 63 gpm (residential).
- CDC — Model Aquatic Health Code, 5th edition (2024), code (opens in a new tab) — Public pools (context only): most pools need a turnover of 6 hours or less.