How to Pick the Right Size Filter for My Pool

Pool filters circulate the water in a swimming pool to remove dirt and debris. Without filters, water would grow stagnant or turn green due to algae buildup. To keep water clean and clear, it's important to size filters correctly to fit your pool. When sizing a pool filter, consider the overall size of your pool as well as the flow rate, then choose a filter that meets or exceeds these requirements.

Things You'll Need

  • Tape measure
  • Calculator
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Instructions

    • 1

      Measure the length, width, and depth of your pool using a tape measure. Multiply these three numbers together to determine the total square footage. For example, a pool that is 10 feet wide by 20 feet long by 8 feet deep would measure 1,600 square feet.

    • 2

      Use this square footage to determine the capacity of your pool in gallons. A standard square foot of water holds 7.48 gallons. Multiply your square footage by 7.48 to find total gallons. For example, a 1,600 square foot pool holds 11,968 gallons of water.

    • 3

      Calculate the flow rate for your pool. Flow rate can be calculated by dividing your pool capacity in gallons by the number of hours you plan to run the filter each day. For example, an 12,000 gallon pool with a filter running for 8 hours a day has a flow rate of 1,500 gallons per hour.

    • 4

      Divide your gallons per hour figure by 60 to determine gallons per minute. A pool with a flow rate of 1,500 gallons per hour would have a flow rate of 25 gallons per minute (GPM). Most pool filter manufacturers use GPM rather than gallons per hour.

    • 5

      Look for filters with a flow rate that meets or exceeds the flow rate of your pool. For example, a filter with a flow rate of 35 GPM is sufficient for a pool with a flow rate of 25 GPM, while a filter with a GPM of 24 would not be sufficient.

    • 6

      Calculate filter flow rate based on square footage information, if needed. Some pool filter manufacturers list flow rate based on square footage of filter area. For instance, the filter may be listed as 12.0 GPM per square foot. In this instance, you'll need to multiply the total square footage of the filter by the flow rate to determine the overall filter flow rate. A filter that measures 4 square feet and has a flow rate of 12.0 GPM per square foot has an overall filter flow rate of 48 GPM.