How Long Does It Take To Fill A Swimming Pool? (With Calculator)

Filling a swimming pool for the first time or after a drain will take quite some time.  If you have a small pool of 5,000 gallons or less you will easily be able to fill it in one day.  For others that are filling a much larger pool it could take multiple days until your pool water has reached capacity.

Assuming your water pressure is pumping at 8 gallons per minute (480 gallons per hour) through your outside water hose, it would take 31.25 hours to fill a 15,000 gallon swimming pool.

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Water pressure is the biggest factor that can make a pool fill much slower or faster.  Your swimming pool can only add water as fast as your faucet will allow.

The average home outside faucet will usually pour somewhere between 4 to 12 gallons per  minute out of the water hose.

To determine exactly how long it is going to take to fill your swimming pool, you must first know a few things about your water pressure and swimming pool.

  •  Find out how many gallons per hours (GPH) that your faucet produces.
  • Determine how many gallon of water you swimming pool will hold to reach capacity.

Once you know these numbers it will be easy to determine a very accurate estimate to the length of time it will take from start to finish when filling your swimming pool.


If you are unsure how many gallons per hour your water pressure pumps through you hose you can find this out quite easily.


Find a gallon water or milk jug and stop watch.  If have a smartphone, you likely have an app that will have a sufficient stop watch.

  1. Have a friend hold the stop watch.
  2. Using the same hose that you will use when filling your pool, place the hose in position to fill the empty jug.
  3. Have your friend start the stop watch at the same time in which you begin filling the water jug.
  4. As soon as the gallon jug is full stop the stop watch.

Simple math can now help you determine the GPH (gallons per hour).


(60 ÷ Y) x 60 = GPH, Y = The number of seconds it takes to fill up 1 gallon of water.

Lets now assume it took 10 seconds to completely fill the jug.

60 ÷ 10 = 6 GPM (gallons per minute).

GPM x 60 = GPH (gallons per hour).

The GPH would be 360 gallons per hour with this scenario.  Once you know what your GPH is, you can easily predict a decent estimate determining how long your pool will take to fill.

Simply divide the number of gallons of water your swimming pool will take by the GPH.


This method could be slightly more accurate since you will be timing a higher amount of water volume.  If you have a 5 gallon bucket, I recommend using this method.

Find a 5 gallon bucket and get your stop watch ready.

  1. Have someone hold a stop watch.
  2. Using the same hose you will use when filling the swimming pool, get it in position to fill your 5 gallon bucket.
  3. Start the stop watch at the exact time that water begins flowing into your bucket.
  4. Once your bucket is completely full, immediately press stop on the stop watch and record the time.


5 gallon bucket water

First divide the number of seconds it took to fill your bucket by the the size of the gallon bucket you were using to determine your GPM.  In this case it was a five gallon bucket.

SECONDS ÷ 5 = Y.  Use the formula below to figure out your GPH.

Assuming it took 50 seconds to fill the 5 gallon bucket your formula would be 50 ÷ 5 =10.  You can now plug that 10 into the formula below to find your GPH.

(60 ÷ Y) x 60 = GPH, Y = The number of seconds it takes for 1 gallon. This again would indicate based on these numbers that you are going to add 360 gallons per hour to your swimming pool.

These are the easiest methods available to determine your gallons per hour and ultimately predicting the length of time it will take in filling your swimming pool.


If you know the dimensions of your swimming pool and the average water depth once filled there is a very simple formula you can use to determine water volume capacity.

The formula to determine your water capacity is different depending on the style of swimming pool you own. They will be classified below in 2 categories. Circular or Rectangle.

Circular pools will include any swimming pool that is in a round shape including oval pools as well.

Rectangle pools formula will apply to any square or rectangle pool. These will mostly be underground swimming pools, but there are some above ground pools in this style as well.


A swimming pool calculator is available by scrolling down to help you determine the volume of water your swimming pool capacity is.


Length in feet x length in feet x average depth in feet x 5.9 = Water capacity.

Lets try a couple examples below in determining the water capacity.

Example 1:  You have a 24 foot circular round swimming pool that is 52 inches deep.  The distance is going to be 24 feet across in all directions.  To determine the volume of water you would simply need to follow the formula.

24  length x 24 length x 4.5 feet depth x 5.9 = 15,292 gallon of water.

Example 2:  You own an oval pool that is 30 feet long at the longest point.  It is also 20 feet across on average from the shortest distance and is 48 inches deep.

30 length x 20 length x 4 feet depth x 5.9 = 14,160 gallons of water.

The formula is quite simple.  Simply L x L x D x 5.9.  This will give you the water volume needed to fill your aquatics and / or swimming pool.


Length in feet x length in feet x average depth in feet x 7.5Water capacity.

I will give a an example for this type of swimming pool in determining water capacity.

Example: Your pool is 30 feet long x 10 feet wide and is 7 feet deep in the deep end. It is 4 feet deep in the shallow end.

30 length x 10 length x 5 feet deep average x 7.5 = 11,250 Gallons. In determining the average water depth I simply average a close middle ground number between the highest and lowest point of the pool. If your pool is more deep and shallow or vice versa you will need to make adjustments accordingly. You may not get exact figures, but will definitely be in the ball park.


Find out how many hours it will take to fill your swimming pool with this simple calculator. Questions with an * are required.

How much does it cost to fill your pool? Check out my other article by clicking here to calculate the average price it will cost to fill your swimming pool.

Pool Fill Estimates Chart

Below is a chart that should also help you in determining about how long you can expect it to take for your swimming pool based on the shown water pressure of Gallons Per Minute.

10 GPM
< 1,000< 2 1/2< 2< 2< 2
5,0001210 3/49 1/48 1/3
10,00023 3/420 3/418 1/216 2/3
15,00035 3/431 1/427 3/425
20,00047 2/341 2/33733 1/3
25,00059 1/25246 1/441 2/3


Now that you have determined your water volume and your water hose GPH you can determine how long it will take to fill your pool and start filling right away,

It is recommended you know precisely how long it will take when you begin the filling process of your swimming pool so you can easily determine how many hours remain before the water reaches maximum levels.

This will allow you to sleep with ease during nap time or overnight without worrying if you swimming pool has a chance of overflowing.

When leaving the hose unattended be sure it is attached in a way that it will not slither out of the pool.  This could cost hundreds of wasted gallons of water that does nothing but soak your lawn and can occur once the water begins to rise.As the water begins to fill, it is best to try and remove wrinkles and bends in the liner prior to the water covering the entire bottom.

Once the bottom is covered with water the weight of the water will take over and it will be hard to remove wrinkles.  At this time the bottom will be shown as it is now for the remainder of the water fill and your swimming season.

If there are other family members using water at the same time your swimming pool is being filled, it may slow down the filling process.

I would recommend avoiding watering the yard or other major use of water during this time.  It will cause your water pressure to decrease making your GPH drop and causing a longer fill time.

Small appliances such as the dishwasher and washing machine will not be enough to affect the pool filling process long term and can be continued as normal without much affect on the total time.

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