4" FDC Tieing into 3" Grid Main

[mcarewm]

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

 

[TravisMack]

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