Media Rate - CPO® Math Tutorial

A Tropical Aquatics Educational Program

Things to know about Media Rate

LEARN HOW TO OPERATE YOUR PUBLIC POOL SPA FACILITY
The flow rate through any filter should not exceed the filter's capacity to handle the water. Filter areas are calculated to handle the maximum possible flow of water through the system.
Pool Media Rate Manufacturer's develop specifications for the amount of water flow through the filter in question. These specifications are governed by standards as established by the National Sanitation Foundation International (NSFI). These standards are referred to as Filter Media Rate also known as FMR. The chart shows the FMR for the various filter types.
Formulas:
  • Filter Area (FA) = Flow Rate (FR) divided by Filter Media Rate (FMR)
    Consider what we have already discussed. Turnover Rate is a minimum code established by health officials for the purpose of maintaining a healthy swim environment. As you saw on the Flow Rate page, Flow Rate calculations are based on Turnover requirements (FR = Gallons ÷ TR ÷ 60). Pumps are sized to provide the Flow Rate to meet Turnover. Now, the filter must be sized to handle the Flow Rate, as pump output. The filter size will depend on the type of filter, or the Filter Media Rate. Therefore, FA = FR ÷ FMR. This will determine the minimum Filter Area for any given Flow Rate.
  • The Filter Area formula may be written so as to express the Flow Rate:
    FR = FA times FMR or FR = FA x FMR
Examples:
  • (1) Your maximum pump output is 275 GPM and you wish to change to a sand filter rated at 15 GPM/sq.ft. filter media rate.
    How much filter area do you need?
    The formula is FA = FR ÷ FMR
    FR = 275 GPM; FMR (from chart and problem) = 15 GPM/sq.ft.
    FA = 275 GPM divided by 15 GPM/sq.ft.
    FA = 18.33 sq.ft.
  • (2) Your pool has a cartridge filter of 851 square feet.
    What is the maximum flow rate allowed?
    The formula is FR = FA x FMR
    FA = 851 sq.ft.; From the chart for a cartridge filter FMR = 0.375 GPM/sq.ft.
We will continue to use a series of "plug-and play" boxes as they are applied in the CPO® class. Just plug the correct number as given by the problem a perform the math (play) as indicated.
The formula for Filter Area is: FR = FA x FMR
FR = x =

Just as a reminder, knowing how to calculate area is important for determining heat loss, sizing pool covers, bather loads in spas, and in some states, bather loads in pools.



Download CPO® Tutorial

Select Math Tutorials