how big is my pool filter


Author: Poolking - Swimming Pool Equipment Manufacturer

When it comes to keeping your pool in top condition, one of the most important components is your pool filter. This essential piece of equipment is responsible for capturing and removing dirt, debris, and other contaminants from your pool water. But how do you know what size filter you need for your specific pool? In this article, we’ll explore everything you need to know about pool filters and how to determine the size that’s right for you.

Understanding Pool Filters

Pool filters work by trapping dirt and other particles in a container filled with some form of media, such as sand, diatomaceous earth (DE), or cartridge. The most common types of pool filters include sand filters, DE filters, and cartridge filters. Each has its own advantages and disadvantages, but they all work to keep your pool water clean and clear.

Sand Filters

Sand filters are the most popular type of pool filter and are often the most affordable. They work by using a container filled with a specially graded sand that captures particles as the water passes through. Sand filters are easy to install and maintain, but they do require periodic backwashing to flush out the collected debris.

DE Filters

DE filters use diatomaceous earth as their media, which is a fine powder made from the fossilized remains of tiny aquatic organisms. DE filters can capture particles as small as 5 microns, making them incredibly effective at filtering out even the smallest debris. DE filters are typically more expensive than sand filters, but they require less maintenance and provide superior filtration.

Cartridge Filters

Cartridge filters use a removable cartridge made of pleated fabric to capture particles as small as 10 microns. They are easy to install and maintain, and they don’t require backwashing like sand filters. However, they do need to be cleaned periodically by removing and hosing off the cartridge.

Determining the Right Size Filter for Your Pool

To determine the right size filter for your pool, you’ll need to consider several factors, including the size of your pool, the flow rate of your pump, and the turnover rate of your water.

1. Pool Size

The first thing you’ll need to determine is the size of your pool in gallons. You can use a simple formula to calculate this: length x width x average depth x 7.5 = total gallons. For example, if your pool is 20 feet long, 10 feet wide, and has an average depth of 5 feet, your total gallons would be 7,500.

2. Flow Rate

Next, you’ll need to determine the flow rate of your pump in gallons per minute (GPM). This information should be included in your pump’s specifications or owner’s manual. If you’re not sure, you can easily calculate it by dividing the total gallons of your pool by the number of hours you run your pump each day. For example, if your pool is 7,500 gallons and you run your pump for 8 hours a day, your flow rate would be 937.5 GPM.

3. Turnover Rate

The turnover rate is the amount of time it takes for your pump and filter to circulate the entire volume of your pool water. The general rule of thumb is to turn over your pool water at least once every 8 hours. To determine your turnover rate, simply divide your total gallons by 8.

Choosing the Right Size Filter

Once you have these three numbers, you can use a simple formula to determine the right size filter for your pool. The formula is: GPM x 60 ÷ turnover rate = minimum filter size in square feet. For example, if your flow rate is 937.5 GPM and your turnover rate is 8 hours, your minimum filter size would be 7.425 square feet.


Your pool filter is a crucial component of your pool’s filtration system. Choosing the right size filter for your pool ensures that it runs efficiently and effectively, keeping your pool water clean and clear. By following these simple guidelines, you can determine the size of filter that’s right for you and enjoy a sparkling pool all season long.


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