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4" FDC Tieing into 3" Grid Main

4" FDC Tieing into 3" Grid Main

4" FDC Tieing into 3" Grid Main

(OP)
Hey all .

I have a single riser for a mall building .  I am coming off
my Grid main to feed my 4" FDC .  My Drop is 4" diameter piping , My Grid Main is 3" .  

do I need to up size my Grid Main to 3" ?  I have checked NFPA 13 2008  8.17.2.3 ....   

My Riser is 4" diameter , so  I am  thinking  I would have to up size the 3" to 4" .  But don't see anything in the Code to determine this .   

any thoughts .

reference to NFPA 2008  8.17.2.3 ,  8.17.2.4.1 , A 8.17.2.4.1

thanks  

RE: 4" FDC Tieing into 3" Grid Main

I would have 4" piping from the FDC to the point it contacts the grid main.  You should be fine at that point.  

It sounds like you have a 4" riser and 4" bulk to your grid main.  So, your FDC is mimicking the automatic supply.

Remember, the FDC is just an augment to the fire sprinkler system, and not a total replacement.  If you have a typical mall, you are talking about 300 - 350 gpm (less if you have a QR reduction) for a total sprinkler demand.

Travis Mack
MFP Design, LLC
 

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