Measure your hose first
Hose flow depends on your water pressure, the hose’s diameter and length, and anything else running in the house, so a number from a box or a forum is a guess. Timing a bucket takes a minute and gives you the real figure:
- Open the tap fully and let it run for a few seconds.
- Time how long the hose takes to fill a bucket of known size, like a 5-gallon bucket.
- Flow in gallons per minute = bucket size ÷ seconds × 60.
A 5-gallon bucket that fills in 30 seconds means 10 gpm. Enter the bucket size and the seconds and the calculator does the rest.
The formula
Hours = gallons ÷ (gallons per minute × 60)
Cost = gallons ÷ 1,000 × price per 1,000 gallons
In metric: hours = litres ÷ (litres per minute × 60), and cost = cubic metres × price per m³.Two hoses only help if they’re on separate taps. Two hoses on one tap split the same flow, so the fill takes just as long.
Worked example
A 15,000 gallon pool, 10 gpm hose, water and sewer at $6 per 1,000 gallons
- Time = 15,000 ÷ (10 × 60) = 25 hours, a little over a day
- Cost = 15,000 ÷ 1,000 × $6 = $90
Fill times for common pool sizes
| Pool | 6 gpm | 8 gpm | 10 gpm | 12 gpm |
|---|---|---|---|---|
| 10,000 gal | 28 h | 21 h | 17 h | 14 h |
| 15,000 gal | 42 h | 31 h | 25 h | 21 h |
| 20,000 gal | 56 h | 42 h | 33 h | 28 h |
| 25,000 gal | 69 h | 52 h | 42 h | 35 h |
| 30,000 gal | 83 h | 63 h | 50 h | 42 h |
Hours to fill 20,000 gallons
Ways to fill faster or cheaper
- Use more than one tap. A second hose on a different outdoor tap roughly doubles the flow if your water pressure holds up.
- Use a short, wide hose. A long, narrow hose loses pressure along its length.
- Ask your utility about sewer charges. Many bills charge sewer on every gallon of water you use. Water that goes into a pool never reaches the sewer, and some utilities give a credit or let you use a temporary meter if you call before you fill.
- Get a quote for a water truck. For a big pool or a slow supply, a bulk water delivery can fill it in hours. Compare the quote with the cost from this calculator.
- Don’t leave it unattended for long. Set a timer for the hour the calculator gives you. An overflowing pool wastes water and can wash out the ground around it.
After the fill
Fresh water starts with no chlorine, no stabilizer and, if it’s from a well, possibly dissolved iron or copper that can stain. Test it before you add anything. The pool chemical calculator works out the start-up doses in the right order, and if you have a salt pool, the salt calculator tells you how many bags to add.
Frequently asked questions
How long does it take to fill a pool with a garden hose?
At 10 gallons a minute, a 15,000 gallon pool takes about 25 hours and a 20,000 gallon pool about 33 hours. Time a bucket to find your real flow rate.
How much does it cost to fill a pool?
Multiply the gallons by your water and sewer rate. At $6 per 1,000 gallons, 15,000 gallons costs about $90. Rates vary widely by town, so use the figure from your bill.
Do two hoses fill a pool twice as fast?
Only if each hose is on its own tap and your water pressure holds up. Two hoses on one tap share the same flow.
Should I fill my pool from a well?
You can, but wells refill slowly and pumps can overheat on a long run, so fill in stages. Test the water for iron and copper first, since metals can stain plaster and vinyl once chlorine is added.
Is it cheaper to fill a pool with a water truck?
Sometimes. A truck saves days of hose time and avoids sewer charges on your bill. Get a delivered price per load and compare it with the cost here.
How do I find my flow rate in litres per minute?
Switch the calculator to metric and time how long the hose takes to fill a bucket of known size in litres. Litres per minute = litres ÷ seconds × 60.
Sources
- Pool Water Efficiency (WaterSense guide EPA-832-F-22-015), September 2022. U.S. Environmental Protection Agency.
Reviewed November 7, 2026. We check the formulas against the sources above and re-run the worked examples whenever we update this page. Found something wrong? Tell us.