Filling a swimming pool for the first time, or after it has been drained, can be a lengthy process. If you own a smaller pool of around 5,000 gallons or less, you may be able to fill it in just one day. However, for larger pools, it might take several days to reach full capacity. A variety of factors can influence the time it takes to fill your pool.
To illustrate, if your water pressure allows for an output of 8 gallons per minute (which translates to 480 gallons per hour), it would take approximately 31.25 hours to fill a 15,000-gallon swimming pool.
Pool Fill Estimates Chart
The chart below provides a helpful estimate of how long it may take to fill your swimming pool based on various water pressure levels measured in gallons per minute (GPM).
| Capacity Gallons |
Hours 7 GPM |
Hours 8 GPM |
Hours 9 GPM |
Hours 10 GPM |
| < 1,000 | < 2 1/2 | < 2 | < 2 | < 2 |
| 5,000 | 12 | 10 3/4 | 9 1/4 | 8 1/3 |
| 10,000 | 23 3/4 | 20 3/4 | 18 1/2 | 16 2/3 |
| 15,000 | 35 3/4 | 31 1/4 | 27 3/4 | 25 |
| 20,000 | 47 2/3 | 41 2/3 | 37 | 33 1/3 |
| 25,000 | 59 1/2 | 52 | 46 1/4 | 41 2/3 |
Understanding Water Pressure
Water pressure plays a crucial role in determining how quickly your pool fills. Your swimming pool can only receive water at the rate your faucet permits. Typically, an outdoor faucet in an average home delivers between 4 to 12 gallons per minute through a garden hose.
To accurately estimate the time required to fill your swimming pool, consider the following:
- Determine the gallons per hour (GPH) that your faucet can produce.
- Establish the total gallons your swimming pool will hold to reach its full capacity.
Once you have these figures, calculating the time needed to fill your pool becomes straightforward.
How to Calculate Your GPH
If you’re uncertain about your faucet’s gallons per hour output, you can easily find out using common household items. Here are two simple methods:
Active Time: 3 minutes
Prep Time: 5 minutes
Total Time: 8 minutes
Difficulty: Easy
Materials Needed
- 1 Gallon Jug
- 5 Gallon Bucket
- Water Hose
Tools Required
- Calculator
- Stopwatch
Instructions
Method 1: Using a Gallon Jug
- Have a friend ready with a stopwatch. This could be a timer app on a smartphone, or you can use a voice assistant like Google Home or Alexa.
- Using the same hose intended for filling your pool, position it to fill a 1-gallon jug.
- Start the stopwatch as you begin filling the jug.
- Stop the timer as soon as the jug is full.
Now, you can calculate your GPH (Gallons Per Hour) using the formula:
(60 ÷ Y) x 60 = GPH
Where Y = the number of seconds it took to fill the gallon jug.
Example: If it took 10 seconds to fill the jug, the calculation would be:
(60 ÷ 10) x 60 = 360 GPH. To find GPM (Gallons Per Minute), simply divide the GPH by 60. In this example, 360 ÷ 60 = 6 GPM.
Method 2: Using a 5-Gallon Bucket
- Have someone else ready with a stopwatch.
- Position the hose in your 5-gallon bucket.
- Have your assistant start the timer as you turn on the faucet.
- Say “Stop the clock” as soon as the bucket is full.
This method with a larger bucket can provide slightly more accuracy. To determine the GPM, use the formula:
(Bucket Size Gallons ÷ Seconds) x 60 = GPM
Example: If it took 50 seconds to fill a 5-gallon bucket, the calculation would be:
(5 ÷ 50) x 60 = 6 GPM. To find GPH, multiply the GPM by 60: GPH = (GPM x 60)
GPH = (6 x 60) = 360 GPH.
Notes
You can use the 5-gallon bucket method with any bucket size; just adjust the numbers accordingly. The results will remain consistent even if you switch between methods.
How to Calculate Your Pool’s Water Capacity
If you know the dimensions and average depth of your swimming pool, determining its water volume is quite simple. The formula varies depending on whether your pool is circular or rectangular.
Circular Pool Water Volume Formula
3.14 x Radius² x Average Depth (in feet) x 7.5 = Water Capacity
Example: For a 24-foot circular pool that is 52 inches deep, the diameter is 24 feet. To find the volume, follow these steps:
1. Determine the radius (diameter ÷ 2 = radius). For this example, the radius is 12 feet.
2. Radius squared = 12 x 12 = 144.
3. Calculate: 3.14 x 144 x 4.5 x 7.5 = approximately 15,260 gallons.
Rectangular Pool Water Volume Formula
Length (in feet) x Width (in feet) x Average Depth (in feet) x 7.5 = Water Capacity
Example: For a pool that is 30 feet long, 10 feet wide, with depths of 7 feet at the deep end and 4 feet at the shallow end:
1. Calculate the average depth: (7 + 4) ÷ 2 = 5 feet.
2. Calculate: 30 x 10 x 5 x 7.5 = approximately 11,250 gallons.
Adjust the average depth as necessary based on your pool’s specific dimensions for a more accurate estimate.
Start Filling Your Pool
With your water volume and hose GPH calculated, you’re ready to begin filling your pool. Knowing the approximate time it will take to fill allows you to plan accordingly and ensures that you can monitor the process effectively.
It’s advisable to keep track of how long it will take for the water to reach full capacity, so you can relax without worrying about potential overflow while you sleep or take a break.
When leaving the hose unattended, ensure it is securely attached in a way that prevents it from slipping out of the pool. This precaution will help you avoid wasting hundreds of gallons of water that could end up soaking your lawn.
As the water fills, it’s beneficial to remove any wrinkles or bends in the pool liner before the water covers the entire bottom. Once the water begins to rise, the weight will make it difficult to adjust the liner, which could lead to permanent creases.
Additionally, if other family members are using water at the same time your pool is being filled, it may slow down the filling process. It’s best to avoid watering your yard or engaging in other major water-consuming activities during this time. However, small appliances like dishwashers and washing machines typically won’t affect the filling process significantly and can run as usual without major impacts on the overall fill time.