FLOW RATE BY PIPE SIZE - The size of your pool piping is a major consideration is setting up or changing your pool equipment. Pipe size determines the maximum flow rate that your pool system will handle. The chart at left shows these flow rates by pipe size. For the more common sizes, 1 1/2" and 2" pipe diameter, the maximum recommended water flow rate is 45 GPM and 80 GPM. If you exceed these rates, you will be overloading your pump's motor. It will be trying to push more water through then the system can handle. You also run the risk of damaging the piping system.
FILTER CAPABILITY.- Filters come in three basic types: Sand , cartridge, and DE. The filtering capacity of these types varies according to their square footage of filtration area. This filtering capacity relates directly to their flow rate.. The sand filters in general have the lowest square footage of filtering material and are in general less able to handle the higher flow rates (GPM). The smaller to mid-size sand filters have 1 to 3 square footage of filtration area which supports 25 to 62 GPM. The larger sand filters have fitration areas of up to 7 sq ft and will support up to about 145 GPM flow rate. The smaller to mid-size cartridge in contrast have filtration areas of 75 to 120 square ft and will support flow rates from 75 to 120 GPM. The typical larger cartridge systems will handle up to 150 GPM. DE filters fall somewhere in between the capability of sand and cartridge in ability to handle flow rate.
FILTER FOOTPRINT - In general, if you have limited space in pool equipment area, go with the cartridge filter. Cartridge filters have a much smaller foot print that either the sand of DE filters.