Pool fill calculator: how long to fill my pool, and what will it cost?

Filling a pool from a garden hose is slow, cheap and impossible to predict without one measurement: how fast your hose actually runs. Water pressure, hose length and hose diameter all change it, so no published figure fits your tap. Two minutes with a bucket and a stopwatch does.

How to time your hose

1. Use the hose you’ll fill with, at its full length, with the tap fully open and no nozzle.
2. Hold it in an empty 5-gallon bucket (or a 20-litre one) and start a stopwatch.
3. Stop when the bucket reaches the 5-gallon (or 20-litre) mark. Do it twice and average.
4. If you’ll run two hoses from separate taps, time each; two hoses split off one tap usually share its flow, so time them together.

How the fill calculator works

hose flow (gpm) = 5 gal ÷ bucket seconds × 60
hours = gallons ÷ (flow × hoses) ÷ 60
water cost = gallons ÷ 1,000 × price per 1,000 gal
metric: L/min = 20 L ÷ seconds × 60; cost = m³ × price per m³
truckloads = gallons ÷ truck capacity, rounded up

A hose that fills a 5-gallon bucket in 40 seconds delivers 7.5 gpm, or 450 gallons an hour. At that rate 10,000 gallons takes about 22 hours and 20,000 gallons about 44 — a weekend on one hose.

What the water costs

• Water. Utilities price it per 1,000 gallons, per CCF (100 cubic feet, 748 gallons) or per m³. The default here is an example; your bill has the real rate, and tiered rates can make a big fill land in a pricier tier.
• Sewer. Many bills charge sewer on every gallon through the meter, even though pool water never goes down the drain. Some utilities offer a pool-fill credit or adjustment, or a separate irrigation meter. Ask yours before you fill — the saving can be larger than the water itself.
• Trucked water. Bulk water haulers deliver by the load. It is faster and spares a well, but usually costs more per gallon than a city tap. Enter their capacity and quote to compare.

Worked examples

Three common fills have their own pages: how long it takes to fill a 10,000 gallon pool with a garden hose, how long and how much to fill a 20,000 gallon pool and how long it takes to fill a 24 ft round pool. If you don’t know the volume, the pool volume calculator and the above-ground pool gallons calculator work it out.

Tips

• On a well, a long fill can draw the well down faster than it recovers. Ask a well contractor about your well’s yield before running hoses for days, or use a truck for part of it.
• Filling a vinyl-lined pool, follow the liner or pool maker’s first-fill instructions; wrinkles are far easier to fix while the water is shallow.
• Measure what goes in. A hose flow meter gives your exact volume. After that, every chemical dose is more accurate.
• Keep it in. Evaporation is the water you pay for again all season; EPA says a cover can prevent up to 95% of it. See the pool evaporation calculator.