What the animation shows
The animation and the step-by-step video above use your numbers. Here is the same walkthrough written out for the default example.
What you enter
- Pool shape: Rectangular.
- Length (diameter for round): 32 ft.
- Width (ignored for round): 16 ft.
- Shallow end depth: 3.5 ft.
- Deep end depth: 6 ft.
- Fill flow rate: 8 gpm. Time a 5-gallon bucket fill: 300 ÷ seconds = gpm.
What happens, step by step
- The hose adds 8 gallons every minute.
- Water runs downhill and collects at the deep end first.
- Now it covers the whole floor, so the level rises more slowly.
- Full: 18,193 gal after 37 h 54 min of filling.
The answer: pool volume is 18,193 gal.
How it’s calculated
- Average depth = (shallow + deep) ÷ 2
- Rectangle: L × W; round: π ÷ 4 × D²; oval: π ÷ 4 × L × W
- Gallons = area × average depth × 7.48
- Fill time = gallons ÷ gpm ÷ 60
Worked example
32 × 16 ft rectangular pool, 3.5 ft to 6 ft deep, filled at 8 gpm.
Inputs
- Pool shape
- Rectangular
- Length (diameter for round)
- 32 ft
- Width (ignored for round)
- 16 ft
- Shallow end depth
- 3.5 ft
- Deep end depth
- 6 ft
- Fill flow rate
- 8 gpm
- Water price per 1,000 gallons
- 0 $/1,000 gal
Results
- Pool volume
- 18,193 gal
- Fill time
- 37.9 hours
Assumptions and limits
- Uniform slope between shallow and deep ends. Hopper-bottom pools hold less.
- Oval treated as an ellipse; oval pools with straight sides hold slightly more.
Verify the result against the applicable local code, adopted code edition, manufacturer instructions and project requirements. See our methodology.
Questions
How many gallons is a 16×32 pool?
At an average 4.75 ft deep, about 18,200 gallons.
How long does it take to fill a pool with a hose?
At 8 gpm, 18,000 gallons takes about 38 hours. Water delivery trucks are faster for large pools.