What Size Filter Do I Need for a Pool?

A pool filter is a critical part of keeping your pool clean. If you choose the wrong size filter, you may incur extra expenses either in paying for more filter than you need or by overstressing your filter, causing extra repairs.

  1. Pool Size

    • The size of the filter you need pool depends on how large your pool is, as measured in gallons.

    Types

    • The three types of pool filters have different filtering rates. According to Pool Plaza, sand filters are capable of 15 gallons per minute (GPM) per square foot, DE filters are capable of 2 GPM per square foot and cartridge filters are capable of about 0.25 GPM per square foot.

    Time Frame

    • The size of your pool filter will also depend on how often you want your pool to turn over. Most pools turn over every 8 to 12 hours. The more you use your pool, the shorter turnover time you will want.

    Calculation

    • Calculate the size of the filter you need by dividing the size of your pool by the number of minutes it should take for your pool to turn over and then dividing the result by the filter rate. For example, an 11,000-gallon pool you wanted to turn over every 11 hours using a sand filter would need an 8.33-square-foot filter.

    Warning

    • Smart Swim Pools and Spas recommends getting a larger filter than the formula would suggest to account for the decreasing efficiency of the filter as it becomes clogged with debris.