Determining the number of gallons needed to fill a swimming pool is an important calculation when installing or maintaining a pool. For a 12×24 foot pool, the gallon capacity will depend on the depth of the pool.
Quick Answer
A 12×24 foot pool that is 4 feet deep will hold approximately 10,980 gallons when filled. A pool that is 5 feet deep will hold around 13,725 gallons. At 6 feet deep, the pool will require 16,470 gallons to fill completely.
Working Out the Math
To calculate the number of gallons for any pool, you need to know the dimensions of the pool and the depth. For a rectangular pool, calculating the volume is straightforward:
- Length x width x average depth x 7.5 = total gallons
The last part of the equation, 7.5, is the number of gallons in a cubic foot of water. So by calculating the total cubic feet of water space in the pool, you can convert that to gallons.
Let’s break down the gallon amount for a few common pool depths:
12 x 24 x 4 Foot Pool
- Length: 12 feet
- Width: 24 feet
- Depth: 4 feet
Volume in cubic feet: 12 x 24 x 4 = 1,152 cubic feet
Gallons: 1,152 cubic feet x 7.5 gallons per cubic foot = 10,980 gallons
12 x 24 x 5 Foot Pool
- Length: 12 feet
- Width: 24 feet
- Depth: 5 feet
Volume in cubic feet: 12 x 24 x 5 = 1,440 cubic feet
Gallons: 1,440 cubic feet x 7.5 gallons per cubic foot = 13,725 gallons
12 x 24 x 6 Foot Pool
- Length: 12 feet
- Width: 24 feet
- Depth: 6 feet
Volume in cubic feet: 12 x 24 x 6 = 1,728 cubic feet
Gallons: 1,728 cubic feet x 7.5 gallons per cubic foot = 16,470 gallons
Gallon Amounts by Depth
Here is a summary of the total gallons needed for various water depths in a 12 x 24 foot pool:
| Depth | Gallons |
|---|---|
| 4 feet | 10,980 |
| 5 feet | 13,725 |
| 6 feet | 16,470 |
| 7 feet | 19,215 |
| 8 feet | 21,960 |
| 9 feet | 24,705 |
| 10 feet | 27,450 |
As shown, each additional foot of depth increases the water volume and gallons required by about 2,735 gallons. Backyard pools are typically between 4 and 8 feet deep on average.
Estimating Gallons for Other Pool Sizes
The same formulas and logic can be applied to calculate gallons for any rectangular pool. Just input the correct length, width, and depth measurements.
For unusually shaped pools, calculating the volume gets a bit more complex. In those cases, it’s best to break the pool down into simple rectangular sections that you can calculate individually. Then add up the volumes for each segment.
Key Factors When Calculating Pool Gallons
Here are some important things to keep in mind when figuring out pool gallons:
- Measure carefully – Any small measurement mistakes will throw off your final gallon total. Measure the length, width, and depth dimensions several times to get accurate numbers.
- Factor in pool shape – Rectangular pools are most common, but also account for freeform kidney shapes or oval pools in your surface area math.
- Consider pool features – If the pool has stairs, benches, or other areas with shallow water, calculate those segments separately.
- Add extra for displacement – The pool structure and any features inside the pool take up some of the space, displacing water. Add 3-5% as a buffer.
- Recalculate before refilling – If refilling an existing pool, measure again as shapes can shift. Also account for any leaks or repairs.
Figuring Out Pool Gallons by Shape
Rectangular pools are the simplest to calculate, but pools can also come in other shapes like ovals, freeform shapes, and more. Here’s how to handle gallons for other pool types:
Oval Pools
For an oval pool, you need to calculate the average length and width. Find the maximum length and width, then the minimum length and width. Add the max and min measurements together and divide by 2 to get the average.
Then simply plug the average length and width into the same gallon formula.
Kidney Shaped Pools
For a kidney or other freeform shaped pool, divide the shape into several manageable rectangles. Calculate the gallons for each rectangular segment individually. Then add up the totals for each section to get the full volume.
Custom Shaped Pools
For the most complex custom pool shapes, it can help to draw the shape on grid paper to scale. Then calculate the volume box-by-box using the 7.5 gallons per cubic foot factor. Add up the gallons from each box to reach the total capacity.
Pool Gallon Calculator Tools
Doing all the rectangular area and volume math by hand can get tedious. For a quicker and easier way to find pool gallons, you can use an online pool gallon calculator tool.
Just input your pool dimensions and depth, and the calculator will automatically figure out the amount of water needed. Here are some recommended pool gallon calculators:
- Calculator.net – Free calculator with automatic gallon amount
- Build Your Aquatic Dream – Includes a pool materials calculator
- Pool Supply World – Handy slider tool to adjust depth
Using one of these pool calculators can save time and make it easy to get reliable volume numbers for just about any pool dimensions. They provide all the formulas and conversion factors needed for accuracy.
Filling Up a 12×24 Pool
Once you know the gallon capacity of your 12×24 foot pool, the next step is filling it up. Here are some logistics to keep in mind for filling a pool of this size:
Water Source
Your available water source will determine the filling process. Options include:
- Garden hose – Cheapest option, but very slow. Would take days to fill a 13,000+ gallon pool.
- Fire hose – Much faster flow rate than a standard hose. Typically used with gas or diesel powered pumps.
- Water truck delivery – Can truck in thousands of gallons treated water to fill the pool quickly.
Flow Rate
No matter the source, the flow rate matters when estimating fill time. Average flow rates:
- Standard 0.5-inch garden hose – 5-10 gpm
- Gas-powered 2-inch fire hose – 150-250 gpm
- Large tanker truck – 500 gpm
Divide the volume by the flow rate to get hours. For example, filling a 13,725 gallon pool with a 250 gpm fire hose would take about 55 hours.
Practical Tips
Other tips for filling a pool efficiently:
- Use a pool cover while filling to prevent evaporation loss.
- Add water clarifier on initial fill to prevent cloudy water.
- Turn on filter pump immediately to circulate and filter new water.
- Test chemicals frequently. Balance pH and shock chlorinate once full.
Draining a 12×24 Pool
During seasonal closings or for repairs, you may need to drain some or all of the water from a 12×24 foot pool. Here are tips for draining efficiently:
Use Main Drain
For fastest draining, use the main drain outlet and open valves fully if available. Main drains often have piping sized for faster drainage than side skimmers.
Supplement with Submersible Pump
For pools without functional main drains or fast enough drainage, you can supplement with a submersible sump pump placed in the deepest area.
Drain to Proper Location
Legally and environmentally, pool water must drain into the sanitary sewer system, not the storm sewer. Some locations may require a permit.
Filter While Draining
Run the pool filter while draining to catch sediment and particles kicked up by draining turbulence.
Time vs. Gallons
An average sized submersible pump may drain 10,000-15,000 gallons per hour. So draining a 13,725 gallon 12×24 pool completely would take around 1 hour.
Refilling a Drained Pool
After repairs or seasonal closure, refilling a drained 12×24 pool takes some preparation:
Inspect Repairs
Check any repairs like resurfacing or plastering have fully cured before refilling. Follow manufacturer instructions.
Clean Surfaces
Scrub all surfaces with diluted muriatic acid cleaner. This removes scale, metals, and buildup.
Check Equipment
Inspect pool equipment like filters and pumps. Replace old sand or DE media. Lubricate valves and o-rings.
Update Chemicals
Acid wash and recharge the chlorinator. Stock up on fresh chlorine or bromine tablets. Purchase new test kits.
Refill Slowly
Refill pool slowly over several days. Use a water clarifier and continuously filter. Check for any leaks.
Cost Factors for Filling a Pool
The costs to fill a 12×24 foot swimming pool depend on:
Water Source
Option 1: Using a garden hose is cheapest (if you have well water), but takes days to fill a large pool.
Option 2: Having water truck delivered and pumped in costs $100-$300 typically.
Option 3: Using high volume fire hoses can cost $50-$150 per day rental fees.
Water Costs
If filling from a home well water source there is no direct cost. But with truck or tap water expect costs of:
- Average water rate $2 to $7 per 1000 gallons used
- Pool filling water rates may be higher
- 13,000 to 27,000 gallons for a 12×24 pool
So total municipal water costs could be $200 to $1000+ depending on local rates.
Equipment Rental
Renting high volume pumps and hoses typically costs:
- Gas powered trash pumps – $50 to $150 per day
- Large fire hoses – $20 to $60 per day
- Hose ramps and accessories – $20 to $50
Expect around $100 to $250 per day in rental fees if using heavy duty pump and hose equipment.
Pool Company Service Call
Having a pool company professionally fill or refill a pool typically costs $100 to $400 as a service call fee.
Maintenance Cost Considerations
Beyond just the initial fill costs, also factor long term maintenance expenses for a 12×24 foot pool:
- Chemicals – $200 to $400 per year
- Electricity – $400 to $800 per year for pumping and heating
- Water – $500+ per year for evaporation replenishment
- Cleaning – $200 to $800 per year for brushing and vacuuming
- Major repairs – $2000+ expenses if equipment like pumps fail
Expect to budget $1500+ annually for proper maintenance of a mid-sized 12×24 foot residential pool.
Conclusion
Figuring out the number of gallons needed for a 12×24 foot swimming pool involves some simple rectangular area calculations combined with the 7.5 gallon-per-cubic-foot conversion factor. For most backyard pool depths, expect 10,000 to 27,000 gallons total capacity.
Use online pool gallon calculators for quick volume estimates. And factor in proper water sources, flow rates, costs, and long term maintenance when installing and maintaining a residential sized 12×24 foot swimming pool.