Floor drain calculations

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britkath

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To calculate the GPM capacity of a floor drain, I found the following equation:
Q = 448.2 Cd A 2gh where Q = Flow Rate (Gallons per Minute)
Cd = Discharge Coefficient (Typically 0.6)
A = Open Area of Grate (ft2)
g = Acceleration (32.2 ft/s2)
h = Head Above the Floor (ft)

What is meant by head above the floor for h? the floor drain is flush with the floor.
 
If I'm not mistaken the head above the floor is the amount of water buildup on the floor. Engineering mumbo jumbo.
 
Get a code book,each size has a dfu (drainage fixtures units)which is how you size it.
 

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