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how do i know what size pool filter to buy



Swimming pools are a great way to cool off and have fun during the hot summer months, but they require regular maintenance to keep the water clean and safe for swimming. One essential piece of equipment you'll need for your pool is a filter. But with so many different sizes and types of filters available, how do you know which one to choose? In this article, we'll go over the factors you should consider when deciding what size pool filter to buy.

Subheading 1: Assess Your Pool Size and Capacity

The first thing you should do is take note of the size and capacity of your pool. These factors will have a significant impact on the type and size of your pool filter. If you have a small pool, with a capacity of fewer than 10,000 gallons, you'll need a small filter with a flow rate of up to 50 gallons per minute. Conversely, if you have a large pool with a capacity of more than 30,000 gallons, you'll need a filter with a much higher flow rate, typically between 150 and 200 gallons per minute.

Subheading 2: Determine Your Filter Type

There are three primary types of pool filters: sand, cartridge, and diatomaceous earth (DE). Each type has its strengths and weaknesses, but the one you choose will have an effect on the size you'll need. Sand filters are the most common, and they're easy to use and maintain. They're also the most affordable and have a longer lifespan. Cartridge filters are more expensive than sand filters, but they offer better filtration and don't require backwashing, so they're a more eco-friendly option. DE filters are the most expensive, but they offer the most effective filtration and are the best choice for large pools. Because of their high efficiency, they can usually be smaller than the equivalent sand or cartridge filter.

Subheading 3: Consider Your Pump Power

The power of your pool pump will also have an effect on the size of filter you'll need. The pump draws water from the pool and forces it through the filter, so if you have a large pump, you'll need a larger filter to keep up with the flow rate. Most filters are sized to match the horsepower of your pool pump, so if you have a one horsepower pump, you'll need a filter that can handle the flow rate of a one horsepower pump.

Subheading 4: Calculate Your Turnover Rate

The turnover rate is the amount of time it takes for the pool's entire volume of water to pass through the filter. The turnover rate is an essential factor in determining the size of the filter you'll need. The industry standard for turnover rate is eight hours, which means the entire volume of water in the pool should pass through the filter once every eight hours. To calculate your turnover rate, divide your pool's capacity by eight. For example, if your pool holds 20,000 gallons of water, you'll need a filter that can handle a flow rate of 42 gallons per minute.

Subheading 5: Check the Manufacturer's Guidelines

Finally, it's always a good idea to check the manufacturer's guidelines for the filter you're considering. The guidelines will tell you the recommended flow rate and the maximum capacity of the filter. By following the recommendations, you'll ensure that your filter is working efficiently, and your pool water is clean and safe for swimming.


Choosing the right size pool filter is crucial for maintaining clean and safe pool water. By considering the size and capacity of your pool, the type of filter you want, the power of your pump, and the turnover rate, you'll be able to select a filter that meets your needs. Remember to follow the manufacturer's guidelines and to perform regular maintenance on your filter to ensure it's working correctly. With the right filter, and regular maintenance, you'll be able to enjoy your pool all summer long.


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