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Interconnection of standpipes

Interconnection of standpipes

(OP)
Hey folks.

I am designing a high-rise mixed use building. The building is primarily a residential apartment building that sits on top of 8 floors of parking. There is also 5 floors of retail\office attached to the parking structure. We will have high pressure standpipes with PRV's in the two stairs that run the full height of the residential tower, and we will have automatic dry standpipes in the two parking deck stairs. In the retail\office portion of the building, we have multiple retail spaces that will be each be supplied off of their own separate control valve.

What we want to do is to tee off of the high pressure standpipe supply with two, 6" Master PRV's in the pump room (to comply with NFPA 14, 2013 ed. 7.2.4(3) ) and use it to supply the retail area sprinkler systems, and the combo standpipe in the 5 floors of office, plus use it to supply the parking deck sprinkler system. Obviously we will have to have an additional FDC down stream of the two Master PRV's, but economically, this seems to be the best route because it saves us a lot of 2.5" PRV Hose valves and control valves for the combo standpipe and retail areas, plus testing ports and a 3" express drain.

My concern is weather or not this design meets the interconnection requirements of NFPA 14 7.5, especially when we look at what the annex to 7.5 has to say about FDC's being arranged to supply all interconnected standpipes.

Your thoughts are appreciated.

RE: Interconnection of standpipes

bmlxd40

At first I though I agreed with your concern, but the more I thought about it I'm not so sure. I assume you have an FDC on your high pressure standpipe per NFPA 14-7.12. If so, why would a second one down stream of the PRV"s be required? I see nothing in the standard that prevents you from using the high zone supply to feed systems/standpipes in the low zone. I could be missing something, but provided the standard does not prevent this, I don't think you have an issue with the interconnected requirement. The only caveat would be if the PRV would be considered a control valve and would violate NFPA 14-6.4.2. No tamper switch is required on PRVs so it seems they would not be considered control valves.

Am I missing something about the arrangement?

Micah Davis
Dynamic Fire Designs
www.dynamicfiredesigns.com

RE: Interconnection of standpipes

(OP)
MicahDavis. The FDC Downstream of the PRV's is required per NFPA 14, 2013 ED 7.2.4 (7)

RE: Interconnection of standpipes

I did overlook note 7 under 7.2.4. It appears your interconnection concern is addressed as the code specifically allows the installation you describe. Reading the applicable codes in light of 7.2.4 (7) and looking again at 7.5, it appears the code is requiring that the FDC provided for the system must be connected to the system side of the PRVs, not that a second FDC must be provided. This makes sense considering the inconsistent performance of PRVs. There is a article in Sprinkler Age magazine that briefly addresses this code section and the circumstances that caused it's creation. (https://sprinklerage.com/nfpa-14-2016-edition/) It concerns the 2016 edition, but the comments are applicable. Just my two cents!

Micah Davis
Dynamic Fire Designs
www.dynamicfiredesigns.com

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