General Drainage through a floor drain question :)

[kelleyl]

I am trying to design for a special shower drainage situation.
I have two showers that together drain 3gpm into a long shallow trench/depression in the floor to a 2" floor drain pipe, 5" square grate strainer.
The CPC says 2DFU for a floor drain, and 2DFU is the equivalent of 1gpm... So I am assuming that means my floor drain will only drain 1gal of water per minute.

So my question is does the shower in at 3gpm minus the drain out at 1 gpm equal 2gpm consistently collecting, or am I missing a key idea? Otherwise this seems it wouldn't work.

Any insight is appreciated!

 

[PEDARRIN2]

The DFU to gpm correlation is general and used to predict flows on a statistical basis. A floor drain will drain more than 2 gpm, even at 2" outlet and 5" square. A 2" pipe at 1/8" slope will flow ~13 gpm before it becomes surcharged. Drains will likely flow more - so don't worry about overflows.