How Long Does It Take to Fill a Pool? Time by Size and Method

How long does it take to fill a pool? A garden hose puts out roughly 5 to 10 gallons a minute, so a 20,000-gallon pool needs somewhere between 33 and 67 hours of running water. That's about one and a half to three days if the hose runs around the clock, and more like two and a half to five days if you shut it off at night. A tanker truck typically carries 6,000 to 8,000 gallons a load and unloads each one in well under an hour, so the same pool is usually full in a day.

The table below gives hours for eight pool sizes at three flow rates, and the bucket test under it tells you which column is yours.

Fill time table by pool size and flow rate

Hours are continuous running time, worked out as gallons divided by flow rate, divided by 60, and rounded to the nearest hour. Tanker loads assume 6,000 to 8,000 gallons per load, rounded up to whole loads.

To turn hours into days, decide how many hours a day the hose will really run. If you run it 12 to 14 hours and shut it off overnight, divide by 13 for a calendar estimate. A 20,000-gallon pool at 8 gallons a minute needs 42 hours, which is 1.75 days running nonstop or a little over three days on a daytime-only schedule.

Not in the table? Divide the gallons by your gallons per minute, then divide by 60 to get hours. A 17,500-gallon pool at 7 gallons a minute comes to about 42 hours. If you don't know your gallons, the quote form works them out from length, width and depth.

Measure your flow with a 5-gallon bucket

On a 20,000-gallon pool, the gap between 5 and 10 gallons a minute is the difference between a long weekend and most of a week, and your flow depends on your water pressure, hose length and hose diameter, none of which you can judge by looking.

1. Connect the exact hose you will use for the fill, at full length, to the spigot you will use.
2. Open the spigot fully and let it run for ten seconds.
3. Time how long it takes to fill a 5-gallon bucket to the brim.
4. Divide 300 by the number of seconds. The result is your flow in gallons per minute.

A bucket that fills in 30 seconds means 10 gallons a minute. At 40 seconds it's 7.5, and at 60 seconds it's 5. At 75 seconds you're down to 4 gallons a minute, below the table, and a 20,000-gallon pool would need about 83 hours. Do the test with the hose stretched out to the pool, because a hose that climbs a slope or runs 150 feet delivers less than it does right at the spigot.

Fill time by tanker (loads and refill trips)

A tanker fill is counted in loads rather than hours. Each 6,000 to 8,000-gallon load usually unloads in well under an hour once the hose is laid, and the time in between is the truck's round trip to its water source.

For a pool of three or four loads, the usual pattern is a morning start and a full pool later the same day, sometimes with a second truck following so the water keeps coming, which matters on new plaster. Our guide to how long a water truck takes to fill a pool breaks a delivery down hour by hour, and the pool water delivery day checklist covers what to have ready.

Two hoses, well pumps and other variables

Two hoses on two separate spigots can roughly halve the time on city water, if the house has the pressure to feed both. Two hoses on one spigot through a splitter share the same supply and gain little.

Hose size and length matter too. A 3/4-inch hose carries noticeably more water than a 5/8-inch one, and every extra 50 feet costs you some flow, so use the shortest, widest hose that reaches.

Pressure also drops on summer evenings when half the street is irrigating, so a hose that tested at 8 gallons a minute at 10am may only manage 6 at 7pm.

Wells are the exception to all of this. On a private well the limit is the well's yield and recovery rate, so a second hose does nothing, and running the pump for 40 hours straight can overheat it or wear it out. Filling in sessions of a few hours, with recovery time in between, can stretch a two-day fill into a week or more, which is the main reason well homes truck the water in. See in-ground pool fills for how a delivered fill runs.

Why fills slow down overnight

The table assumes the hose never stops, and real fills stop all the time.

People shut the hose off at bedtime because they worry about overflow, a hose popping off the spigot, or a wet basement if the spigot is near the foundation. Someone kinks the hose moving a lawn chair. The sprinklers come on at 5am and pressure drops for an hour.

Each pause adds hours. On new plaster or pebble a pause does more harm than slow flow, because water sitting at one level on a curing finish can leave a visible ring, which is why builders ask for a continuous fill. The complete pool fill guide covers how to set up a hose fill so it can run unattended safely.

What two days of hose time actually costs you

The hose is usually the cheaper option on city water, but it isn't free, and the water is only part of the cost.

• The water bill. Look up your utility's rate per 1,000 gallons and multiply by your pool volume in thousands. Check whether sewer is billed on water use, because some utilities credit the sewer portion of a pool fill if you call first. On a tiered rate, a large fill's gallons can also land in the higher-priced tiers.
• Your time. Someone has to be home to check the hose every hour or two for several days.
• Risk on new finishes. Pauses can leave ring lines on plaster, and an uncovered hose end can leave stream marks.

Against that, a tanker fill of a 15,000 to 30,000-gallon in-ground pool is usually 2 to 5 loads, and it's done in a day. Above-ground pools usually take 1 to 3 loads. These are estimates, and your quote gives one delivered price.

If you're on city water with an existing finish and no deadline, use the hose. If you're on a private well, have new plaster, a party on Saturday or no outdoor tap, a truck makes more sense. The trucked water versus hose comparison has the side-by-side.

Frequently asked questions

How long does it take to fill a 20,000 gallon pool?

By hose, it's 33 to 67 hours of running water depending on your flow rate, which is about two and a half to five calendar days if you shut the hose off overnight. By tanker it's 3 to 4 loads of 6,000 to 8,000 gallons, usually done in one day.

How long does it take to fill a 15,000 gallon pool?

At 10 gallons a minute it takes about 25 hours of running water, at 8 about 31 hours and at 5 about 50. A tanker does it in 2 to 3 loads, typically the same day.

Can I leave the hose running overnight?

On an existing finish, with the hose end well inside the pool, many people do. The risks are overflow if you misjudged the time, and a hose that pops off the spigot and runs into a basement window well. A hose timer set to shut off at your calculated hour takes care of most of that.

How long does it take to fill an above-ground pool?

By hose, a 5,000-gallon above-ground pool takes about 8 to 17 hours and a 12,000-gallon one 20 to 40 hours. By tanker, those two sizes take 1 and 2 loads, and most above-ground pools take 1 to 3.

For most in-ground pools, that's several days by hose against a single day by truck. Send the ZIP and the gallons and we will send you the delivered price so you can compare the two with real numbers.