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what size pool filter do i need for my pool


Author: Poolking - Swimming Pool Equipment Manufacturer

What Size Pool Filter Do I Need for My Pool?

If you are the owner of a swimming pool, you want to ensure that the water is clean, clear, and safe for swimming. The key to a successful pool maintenance routine is having the right equipment, particularly a pool filter. But what size pool filter do you need for your pool? This guide will help you determine the best filter size based on your pool's size and usage.

1. Types of Pool Filters

Before we dive into filter size, it's important to understand the different types of pool filters available. There are three main types: sand filters, cartridge filters, and DE (diatomaceous earth) filters. Sand filters are the most common and affordable, but they require more maintenance than cartridge or DE filters. Cartridge filters are easier to maintain but can be more expensive upfront. DE filters provide the best filtration, but they require more maintenance and are typically the most expensive.

2. Pool Size and Gallons

The first factor to consider when determining the right size pool filter is the size of your pool. To calculate the number of gallons in your pool, use the following formula:

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, the calculation would be:

20 x 10 x 5 x 7.5 = 7,500 gallons

3. Pool Usage

Another factor to consider when choosing a pool filter is how often the pool is used. If you have a high-traffic pool, such as a public pool or a pool used frequently by family and friends, you will need a larger filter. A filter that is too small for the pool's usage will not be able to keep up with the demand and may result in cloudy or dirty water.

4. Flow Rate

Flow rate is the amount of water that flows through the filter in a given amount of time, usually measured in gallons per minute (GPM). The flow rate for a pool filter should be based on the turnover rate of the pool, which is the amount of time it takes for the entire pool's water to be filtered. For example, if you have a 7,500-gallon pool and want a turnover rate of eight hours, the calculation would be:

7,500 / 8 = 937.5 gallons per hour (GPH)

To convert GPH to GPM, divide by 60:

937.5 / 60 = 15.6 GPM

5. Matching Filter Size to Flow Rate

Once you know your pool's size, usage, and desired flow rate, you can determine the appropriate pool filter size. In general, a filter's size should match the pump's flow rate in GPM. For example, if your pool's flow rate is 15.6 GPM, you should choose a pool filter with a flow rate of 15 GPM or higher.

It's important to note that a filter that is too large for your pool can be wasteful and may not work effectively. A filter that is too small will not be able to handle the water volume and will require constant maintenance.


Choosing the right size pool filter is critical for maintaining a healthy and safe swimming pool. Consider factors such as pool size, usage, flow rate, and filter type to determine which filter size is best for your needs. With the right pool filter and maintenance routine, you can enjoy crystal clear water all summer long.


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