OK to Combine Sprinkler/Standpipe Dry System?

12/5/2025

Is there an NFPA 13 or 14 restriction for a combined sprinkler - standpipe dry system?

This is an open parking structure. Thanks in advance.

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9 Comments

Dan Wilder

12/5/2025 08:15:20 am

Definitely not a preferred method but if you can comply with NFPA 13 & 14 & get the AHJ buy-in, nothing directly prevents it that I am reading (mostly annex materials and interpretations) ....

Some items that I can see being an issue would be the water delivery time (if the system is big enough) as a dry standpipe is allowed up to 3 minutes for water delivery, well beyond the 60 second requirement.

A heated valve room is also required for all the valves.

Not sure there is a way to prime a dry valve without water (there may be, but I've never heard of it).

Back to water delivery, that is a lot of air to displace prior to a valve activation. Even with no mandated water delivery time, the intent of delivery time is that a 500 gallon (or 750 with a QOD) would still be relatively quick.... certainly not 3-5 minutes after sprinklers start fusing. Also, an open 2.5" valve expelling air vs what would start as one sprinkler will have a major impact on that reduction in air pressure and trip time.

FDC tie in could be problematic.

Helena Vrettou

12/5/2025 08:38:18 am

There are worse in this project. The Fore Hoses are connected simply, on the feed pipes not the sprigs (thank God) but simply on the sprinklers pipes like a normal hose bib.
The firehoses are named as class II but I see"mop" fire hoses not the listed ones.
The dry valves and all, compressors etc.are in the basement, the parking has 5 storeys of 12500sq.m each, two risers !
I am desperate. If this is acc.to NFPA I am an astronaut...
What is your opinion?

Brett

12/5/2025 09:00:15 am

Helena,

Are you the original poster?

It sounds like this is an existing system. Are the hose valves connected to the sprinkler system piping or is there a separate standpipe system?

Pete H

12/5/2025 09:12:54 am

Can you FOIL the original design plans to see if this was submitted to an AHJ or if this was just installed wild wild west style?

Anthony

12/5/2025 08:47:35 am

I do not recommend this. Get a 'hot room' in a convenient location and run a dry system out from there. The delivery times with those larger pipes needed for standpipe flow will substantially slow down your delivery time.

I think the compliance issue will come from volume limitation at 750 gal for any NFPA 14 dry valve. 450 feet of 6'' = 742 gal (sch 10).

Glenn Berger

12/5/2025 09:05:03 am

Are you trying to combine an Automatic Dry Pipe Sprinkler System with a Automatic Class I Dry Standpipe System????

Helena - If this is your project, you need to seek out the advice of a legit FPE for assistance and possibly turn the design over to them. There are lots of problems here.

Jesse

12/5/2025 09:10:59 am

Combined wet AS and SP systems are not uncommon at all. While I can't see a code reason that says no, I wouldn't recommend this for a bunch of reasons

Jack G

12/5/2025 11:06:18 am

If this is a nfpa 14 combined system and follows the rules, then yes.
In this set up the combined system a single riser feeds both the hose valves and the sprinkler system on each floor.
Floor maniolds with check valves branch off at each floor.. check prevents water from draining back into the standpipe.
Water supply must meet , must be sized to meet the combined hydraulic demands of both the standpipe hose and the sprinklers.
Air vs Water
NFPA 14 specifies which. standpipes can be combined(,(;automatic dry, automatic wet, ) and which cannot (manual dry, semi.automatic dry.
So yes its feasable..

Pete H

12/5/2025 12:09:54 pm

Really this does lead us to the question:

"Manual or Automatic?"

...I really hope not manual. Manual Dry Standpipes are supposed to be super rare.

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OK to Combine Sprinkler/Standpipe Dry System?

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