When selecting a pool filter, you must first choose what type of filter to buy. The choices are cartridge, diatomaceous earth (DE) and sand filters.
Sand Filters
Sand filters are the easiest to maintain as well as being the most affordable. They never need chemicals to stay clean, yet remove medium to large particles for a relatively clean pool. To calculate the size needed, simply use the formula below:
Pool Volume (gallons) / 780 minutes / 15 = Minimum Sand Filter Area Needed
DE Filters
DE filters use diatomaceous earth powder to capture even the tiniest contaminant particles with ease, giving you jewel-like water quality that other filters cannot match. They also never need chemicals, but require more complicated cleaning than sand filters. To calculate the size needed, simply use the formula below:
Pool volume (gallons) / 1.5 = Minimum DE filter Area Needed
Cartridge Filters
Cartridge filters are the true middle of the road option, offering filtering performance between sand and DE filters as well as requiring only slightly more maintenance than both. Their filter elements are easily replaced to restore filtering efficiency, and these elements can usually be cleaned by spraying with a garnen hose. They come in a wide variety of sizes to fit virtually any pool, large or small. To calculate the size needed, simply use the formulas below:
Pool Volume (gallons) / 780 minutes = Gallons per Minute (GPM)
GPM / 0.375 = Minimum Cartridge Area (If between sizes, it is recommended you go with the higher size)