Calculating your pool size
Before you can go shopping or test your water, you need to know the amount of gallons that your pool can contain. Find your pool type in the following sections, and then use the associated formulas to help calculate your pool’s volume.
For square or rectangular pools that have a single depth
You use this simple formula to calculate the volume of a square or rectangular pool that has only one depth:
Length x Width x Depth x 7.5 = Volume in Gallons
For example, say you have a 12-foot-by-24-foot rectangular above ground pool that has a water depth of 4 feet. Here’s the calculation to determine its volume:
24 feet x 12 feet x 4 feet x 7.5 = 8,640 gallons
For square or rectangular pools that have multiple depths
You can calculate the volume of a square or rectangular pool that has multiple depths in two ways, depending on how the depths are separated. Here’s how to do it for gradual-depth and drop-off separations:
A pool that has gradual depth change:
If your pool has a gradual decline to your deep end, you’ll want to use this equation:
Length x Width x Average Depth x 7.5 = Volume in Gallons
Use this formula to calculate the average depth of your pool:
(Shallow End Depth + Deep End Depth)/2 = Average Depth
Here’s an example: You have a 16-foot-by-32-foot inground pool that has a 3-foot shallow end and 8-foot deep end. First, you calculate the average depth:
(3 feet + 8 feet)/2 = 5.5 feet
Then, you plug your numbers into the volume equation:
32 feet x 16 feet x 5.5 feet x 7.5 = 21,120 gallons
So this pool can hold 21,120 gallons of water.
A pool with a drop-off:
If your pool has two distinct depths separated by a drop-off, then you treat the pool like two separate pools, using the formula for a pool that has only one depth (Length x Width x Depth x 7.5 = Volume in Gallons), and then add them together.
For example, say you have a 15-foot-by-30-foot inground rectangular pool that has a shallow end on each side of the pool measuring 5 feet long by 15 feet wide by 3 feet, and a deep end measuring 5 feet long by 15 feet wide by 8 feet deep in the center of the pool.
First, you calculate the volume for one of the shallow ends:
5 feet x 15 feet x 3 feet x 7.5 = 1,687.5 gallons
Then, you calculate the volume of the deep section in the middle of the pool:
5 feet x 15 feet x 8 feet x 7.5 = 4,500 gallons
Now, add together the two shallow ends and the deep section in the middle:
1,687.5 gallons + 1,687.5 gallons + 4,500 gallons = 7,875 gallons
This entire pool has a volume of 7,875 gallons of water.
For round pools
Calculating the volume for a round pool takes a little more math work. Here are the math concepts at play in this formula:
- Pi, which is a number used in calculations involving circles, is rounded to 3.14 for this calculation.
- Radius is defined as half the diameter (and the diameter is a straight line that passes through the middle of a circle).
- When a number is squared, it’s multiplied by itself.
Now that we have all that math stuff out of the way, here’s the formula you use to calculate the volume of a round pool:
Pi x Radius Squared x Average Depth x 7.5 = Volume in Gallons
Here’s an example: You have a round pool that’s 24 feet in diameter and has a 4-foot water depth.
First, calculate the radius:
24 feet/2 = 12 feet
Now, calculate the radius squared:
12 feet x 12 feet = 144 feet
Plug your numbers into the original equation:
3.14 x 144 feet x 4 feet x 7.5 = 13,564.8 gallons
This round pool can hold 13,564.8 gallons of water.
Springtime shopping list
Getting your seasonal supply of chemicals in the spring can save you time and, hopefully, money. Here’s a check list of things to remember to get:
- Sanitizer: Start with your sanitizer, whether that’s chlorine tablets, salt, bromine, or a biguanide sanitizer, depending on what you use.
- Shock and algaecides: Get a season’s supply of your favorite oxidizing shock products and your algaecides.
- Alkalinity increaser and calcium hardness increaser: You won’t know the exact amount of these products to get but start with about 1 pound of each product per 1,000 gallons of water in your pool. (For example, a 10,000-gallon pool would get 10 pounds of each.)
- pH increaser and decreaser: Grab a small container of both pH increaser and decreaser.
- CYA: Get at least 5 pounds of cyanuric acid (CYA) for any size pool. It is a good place to start!
- Test strips and filter media: Don’t forget to pick up new test strips and filter media (depending on what type of filter you have, such as diatomaceous earth or sand).
Creating a weekly maintenance schedule
Keeping your pool in tip-top shape can seem overwhelming, so here’s a simple checklist of what you want to try to do weekly (or as needed):
- Test your water. Testing is key to keeping your pool clean, clear, and safe for bathers. At a minimum, a water test should be done weekly. Most people choose Sunday afternoon/evening because you’ll need to shock the pool after testing, and most people are done swimming for at least a few days by Sunday evening.
- Add shock and algaecide. Add these chemicals to your pool weekly; you can add them in right after you test your water.
- Vacuum your pool. Vacuuming will help prevent algae growth or staining from things left on the floor of the pool. A weekly vacuum session tends to be enough, and you can do this chore any day of the week.
- Brush down the pool. This is an important part of maintenance and preventing algae growth. I’m aware that brushing isn’t the most fun task, but if you can do it right after vacuuming, you’re golden for the week.
- Skim the surface of your pool as often as you want. Do this task more frequently if there’s a lot of tree debris falling into your pool so that your skimmer baskets don’t get clogged too quickly.
- Don’t forget to clean your baskets. Your skimmer and pump basket accumulate quite a lot of debris over the week, so I recommend checking them as often as possible, but at least two times a week. This frequent checking (and emptying when they’re getting full) will prevent them from becoming clogged and possibly damaging the system.
- Check your filter pressure. Pay special attention to your filter pressure if you have a diatomaceous earth (DE) filter. Those filters can clog quickly, and a 4 to 6 pounds per square inch (psi) increase on your gauge is enough of a change to warrant a backwash. Sand and cartridge filters typically must be cleaned less frequently, but still check them weekly.
