How Much Does It Cost To Fill A Swimming Pool With Water? (With Calculator)

A pool shaped like a dollar sign.

One of the highest initial costs of owning a swimming pool is adding water to it. This is especially true for brand new installations that don’t yet have any water added and will require thousands of gallons of water to completely fill.

There are also costs associated for pool owners that are re-opening their pool in spring from a previous season. Many pools are partially drained below the skimmer to prevent water pipes and hoses from freezing. Depending on the size of pool, this could be several hundred to likely into the thousands of gallons of water that need replenished after a winter break.

It costs between $4 and $10 per 1000 gallons of water on average that is used in your home. When it comes to filling a swimming pool after installation, it could take just a few thousand to over 20,0000 gallons of water depending on your pool size. An empty swimming pool could cause a charge of anywhere between $75 to over $200 for an average size pool to be filled.

Swimming Pool Water Capacity

Before you can determine how much it is going to cost to fill your pool up, you will need to determine how many gallons of water your swimming pools capacity is.

One of easiest ways to determine this is the material that you receive from the manufacture of your pool after purchase. If you do not have access to that information, a simple math calculation can help you determine your swimming pools water capacity.


To determine how much water your swimming pools capacity is, simply use the formula below according to the style of pool you own.

I have an older article “How long will it take to fill my swimming pool” that you may also be interested in. Click here to check it out.

Circular Pools

For circular style pools including round and oval, you need to fill in the blanks below to calculate how much water the pool capacity is.

Length (A) x Length (B) x Depth x 5.9 = Total Water Volume

If your pool is round length A and length B should be the same. If your pool is oval, those numbers will vary, since there is a longer part of the pool and a shorter portion.

Rectangle Pools

For pools that are square and rectangle, the formula is slightly different. For these types of pools use the formula below to determine water capacity.

Length (A) x Length (B) x Depth x 7.5 = Total Water Volume

If your pool as shallow and deep ends, you will need to put the average water depth in the Depth column to get a fairly accurate water volume capacity with this calculation.

Determine Cost

Below is a chart based on a water cost of $9 for every 1000 gallons of water it requires to fill your pool. Your water cost may be higher or lower. Use the calculator above if you know your exact rate to get a better estimate of water costs.

Gallons Of
Cost To Fill
With Water

Once you know the total number of gallons your swimming pools capacity is, all you need to determine is the rate of your water / sewer charges to get a good idea how much it will cost to fill up your swimming pool.

For people that are on city water you should be able to find this information on your water bill or their website.

We will use my current water rate as an example to determine how much it would take to fill a pool of about 20,000 gallons of water.

My Water Bill Rates

In Midwest City, Ok according to their website as of January 7, 2019 your first 0-2000 gallons of water is included in the initial charge of your water bill. This means you are charged for a minimum of 2000 gallons whether you use 0 gallons or 2000. The same applies to sewer rates as well.

Residential water rates show to be $4.11 per 1,000 gallons of water.

Since the base charge is mandatory each month we will not add those charges to the cost of filling the pool.

Once the 2000 gallons of water has been used there is a $4.11 charge per every 1000 additional gallons of water and a $4.28 charge per 1000 gallons of sewage use. Although filling the pool will not affect the sewer, my city will still charge it even when filling a swimming pool. Check with your city to see if you may be able to get an exemption from sewage, however most do not.

All I need to do is add the sewage fee and water fee which is $4.11 + $4.28 = $8.39 and no that for every 1000 gallons of water I use, it will cost me $8.39.

For a 20,000 gallon pool being filled the additional charge that will be added to my water bill would be $167.80. (20,000 Gallon/1000) X $8.38 = $167.80. My water bill will charge me $8.39 for every 1000 gallons of water used.

(Pool Capacity In Gallons/1000) x Cost Per 1000 Gallons

Formula to determine how much it will cost to fill your swimming pool.

Water Wells

Some people may be using a water well instead of city water. If this is the case you do not have have a water bill, however your electricity is used when running your well pump.

When filling a swimming pool for an extended period of time, the well pump will use much more electricity and you can expect your electric bill to rise.

All you need to do is determine how much electricity it uses per 1000 gallons of water and determine the price per thousand and you can also use the above formula to find out how much your electric bill will increase.

In determining this, you will need to know your well pump manufacture, watts and model to find this information. Most well pumps are going to cost less than that of city water, although there will be exceptions.

If you do not know how much per 1000 gallons of water it costs you in additional electricity, you can safely use the price of my water and that will get you a good idea and may even be higher that what it will cost you. Remember I have to pay sewer fee’s, well pump owners do not.

Partial Fills

If you are only refilling your pool from a partial drain below the skimmer, you probably only have to fill between 15% of the pool volume. In other words if you have a 20,000 gallon pool, expect to top off about 1000 to 3000 gallons of water depending on how low the water levels are.

Also during the regular season you will have to replenish water in the pool from evaporation, an occasional leak and fun splashes that take place in the summer time. These type of refills shouldn’t be all that noticeable on your everyday bills.

Use A Tape Measure

Tape measure that is measuring how low the water level is from the top of the pool.

You can easily determine how many gallons of water your partial fill will take as well as the added costs you can expect on your next dreaded water bill.

All you need to do is measure the distance from the surface of your water and the top of the swimming pool in which you plan to fill the water to. If you have a cover on your swimming pool, measure this before you remove the cover. You can place the end of the tape measure on the cover and then determine the distance between the cover and the top of the pool.

If you find it is 1.5 feet from the cover to the spot you expect to fill your water up to, plug that in the formula calculator. The depth will be the same for all sides of the pool so it will be easy to determine how much it will cost to fill your partially empty pool.

A pool is fun, rewarding and a great family activity, but this will hopefully help you from receiving an unexpected charge from filling your swimming pool. Now fill it up and go swim!

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