Filter System Flow Rate Calculator

Filter Flow Rate Calculation

All filter media has optimum flow rates where that media will perform the best and provide the best water filtration performance. This flow rate can be measured in the amount of gallons per minute that can flow through one square foot of filter media square area.

Step 1 – Enter the Tank Diameter.  Common tank diameters for residential and small commercial applications are 9″, 10″, 12″, 13″, 14″, 16″, 18″, 21″, 24″ and 30″.

Step 2  –  Enter the “Service Flow Rate”.   The service flow rate is the flow rate the filter media can filter at maximum filtration efficiency.   This also can be thought of as the ‘continuous flow rate', if the filter were to be used for more than intermittent usage, such as filling a storage tank, or in irrigation applications where the water might run for an hour or more.

Step 3 –  Enter the “Maximum Flow Rate”.  This is the maximum flow rate, (gallons per minute) that can flow through the media, per square foot of filter area.   Enter the flow rate from the chart below based on the type of filter media used.

Step 4 – Enter the “Backwash Flow Rate”. Use the chart below to enter in recommended values for common filter media. Backwash flow rate is important, as the filter media must be able to backwash at the correct flow rate to assure it is properly cleaned and restored. Inadequate backwash flow can result in the filter media becoming fouled.

Step 1 Enter the Tank Diameter in inches:
Step 2 Enter the Service Flow Rate in gallons per minute
Step 3 Enter Maximum Flow Rate in gallons per minute
Step 4 Enter Backwash Flow Rate in gallons per minute
Filter Tank Media Surface Area in Square Feet
Service Flow Rate in gallons per minute
Maximum Flow Rate in gallons per minute
Backwash Flow Rate in gallons per minute

Suggested Flow Rates for Common Filter Media in GPM Per Square Foot of Filter Area

Filter Media Service Flow Rate Max Flow Rate Backwash Flow Rate
Activated Carbon 5 7 10 to 12
Anthracite 5 7 12 to 18
Birm 3.5 5 10 to 12
Calcite/Corosex 3 6 8 to 12
ChemSorb 5 7 8 to 10
Filox 5 10 12 to 20
Filter Sand 2 5 15 to 20
Filter-Ag 5 6 8 to 10
KDF 10 15 25 to 30
Manganese Greensand 3 5 8 to 10
MangOX 5 10 12 to 22
MTM 3 5 8 to 10
Multi-Media Depth 5 10 13 to 18
Pro-OX 5 10 12 to 22
Pyrolox 3 5 25 to 30


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