How Long Does It Take to Fill a Pool?
Quick answer: pool gallons ÷ gallons per minute = fill time. A standard garden hose delivers 8–12 gpm, so a 15,000-gallon pool takes about 21–26 hours through one hose — or 3–5 hours through a 2-inch supply line.
- The fill time formula
- How fast does your hose flow?
- Fill time by pool size
- Speed matters: filling too fast
- Worked example: 15,000-gallon pool
- FAQ
The fill time formula
Fill time is a straight division: pool gallons ÷ water flow (gallons per minute) = minutes to fill. Convert to hours by dividing by 60. You need your pool's volume (use the pool volume calculator or your pool's rated gallons) and your actual hose flow — the rate printed on a bucket test beats any estimate.
How fast does your hose flow?
At typical residential pressure (40–60 psi), a 5/8-inch garden hose delivers about 8–12 gpm. A 3/4-inch hose flows 15–18 gpm; a 1-inch or larger line much more. Measure yours: time how long a 5-gallon bucket takes to fill and divide 5 by that time in minutes. If it fills in 30 seconds, you're at 10 gpm.
| Pool size | @ 10 gpm | @ 20 gpm | @ 50 gpm (2-in line) |
|---|---|---|---|
| 5,000 gal | 8.3 hrs | 4.2 hrs | 1.7 hrs |
| 10,000 gal | 16.7 hrs | 8.3 hrs | 3.3 hrs |
| 15,000 gal | 25 hrs | 12.5 hrs | 5 hrs |
| 25,000 gal | 41.7 hrs | 20.8 hrs | 8.3 hrs |
Speed matters: filling too fast
Don't just crank the water on. Filling too fast can float a vinyl liner, wash out the pool base, or stress a gunite shell. General practice: fill with a single garden hose for small pools, and keep a gunite pool at no more than about 1 inch of water per hour. Check with your municipality on fill permits and water rates for large first fills.
Worked example: a 15,000-gallon pool
- Hose flow = 10 gpm (measured bucket test)
- 15,000 ÷ 10 = 1,500 minutes = 25 hours
- Running 2 hoses → 12.5 hours
- With a 2-inch supply line at 50 gpm → 5 hours
FAQ
Divide pool gallons by your fill rate. A standard garden hose delivers 8–12 gpm, so a 15,000-gallon pool takes about 21–26 hours through one hose. A 2-inch supply line fills the same pool in 3–5 hours.
About 8–12 gallons per minute at typical residential pressure through a 5/8-inch hose. A 3/4-inch hose flows up to 15–18 gpm. Measure yours by timing a 5-gallon bucket.
About 21–26 hours through one standard garden hose at 10 gpm. With a 2-inch line at 50 gpm it's 5 hours. Running two hoses halves the time.
About 7–10 hours through one standard garden hose at 8–12 gpm. An above-ground 5,000-gallon pool typically fills in under a day with one hose.
Yes — filling too fast can float a vinyl liner, wash out the base, or crack a concrete pool. Fill with a single garden hose for small pools, and keep a gunite pool at no more than about 1 inch per hour.