How are filters sized?
Start with the total volume in gallons and divide by the desired turnover in minutes to get the design flow rate. Since most filters are designed to run at a maximum of 15 gallons per minute per square foot, simply divide the design flow rate by 15 to arrive at the minimum amount of filtration area needed. Then consult filter data tables to consider which options are best. Note that most health departments require a six hour turnover (360 minutes) for standard pools, but many pools—especially those designed for shallow water recreation—should have turnovers of four hours (240 minutes) or less to adequately clean the water.
