Separate Sprinkler, Standpipe Risers "Combined"?

5/11/2022

We have a series of highrise buildings where an NFPA 13 sprinkler system and a wet standpipe system (NFPA 14) are to be installed.

If the sprinkler and the standpipe systems are supplied by a common fire pump, and horizontal supply pipe, but have separate vertical risers, will the system be considered a combined system?

Will the subsection of NFPA 14 (2019 Edition) section 7.10.1.3.1.1 apply?

7.10.1.3.1.1 In a building protected in accordance with NFPA 13 or NFPA 13R, the water supply for the combined sprinkler and automatic standpipe system shall be based on the sprinkler system demand (including any hose stream demand) or the standpipe demand, whichever is greater.

The buildings are fully-sprinklered, and the proposed fire pump is rated at 1,000 gpm. There is a water storage tank of 30,000 gallons. Thanks in advance.

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7 Comments

schulman

5/11/2022 08:12:41 am

yes.
and yes.

Jesse

5/11/2022 08:24:58 am

Yes indeed, its combined system and yep NFPA 14 7.10.1.3.1.1 applies.

Glenn Berger

5/11/2022 08:29:28 am

You have a combined system.

Dan Wilder

5/11/2022 08:35:56 am

Lots of info so lets take some bite size answers...

Series of high rises fed from a common pump and horizontal distribution piping network with vertical standpipes within each high rise.

So you are describing some sort of lower podium style parking/retail space with individual high rises on top correct? Each of the high rises should be their own building via a horizontal separation between the podium and towers and the towers should have the correct distance between.

With that, yes, each system is a combined system but only for the individual building they are supplying. The high rise will have a vertical standpipe(s) with sprinkler risers, the podium will have more of a horizontal standpipe(s) with sprinkler risers and all will need separate hydraulic calculations to prove them.

Yes, the 7.10.1.3 for combined systems would apply for your situation.

I do believe that the tank size mentioned is undersized based on the fact that any tank will have inherent volume that is unusable based on location of the vortex plate and normal fill line vs the actual top of the tank (and it's a true auxiliary water supply). Yes, this complies with the 30 minute requirement per 9.2 but may be undersized for a 13 system for a OH system requiring >500GPM for the required 60 minutes (like a roof top mechanical room).

5/12/2022 02:04:29 am

Hi Dan,

The project is exactly as you described, a common basement used primarily as parking area and high rise buildings above.

Some project stakeholders argue that in order to qualify as combined system, the vertical standpipe for the high rise buildings shall be common for both the sprinkler and standpipe [single vertical pipe supplying both the hose valves and sprinkler system as shown on NFPA 14 (2019): Figure A.6.3.5 (a) & (b). And since the vertical pipes (risers) are separate, it is not a combined system thus the fire pump and fire water tanks required for the sprinklers and standpipes are to be added.

The design for separate vertical supply pipes is to eliminate the pressure reducing valve on lower levels as the pressure will exceed 175 psi (one PRV is to be installed on each vertical supply pipe of the sprinkler systems).

AHJ position for this matter is to cite an specific NFPA 14 section or clause that separate risers can be qualified as combined system and it will be accepted.

Alex

5/11/2022 08:48:46 am

Hi,

I was thinking the same as Dan. Do you have multiple buildings as Dan described or was that simply a general point saying you have seen this design within multiple buildings?

Like others have mentioned above, you do have a combined system.

Alex

Todd E Wyatt

5/11/2022 09:00:28 am

Regarding the discussion of "podium" buildings ... 2021 IBC Section 510 Special Provisions describes (8) conditions that exempt or modify the allowable building heights and areas based on the Occupancy Classification (OC) and the Type of Construction (TC).

Depending on the stacked OC & TC special conditions, the different OC portions of the building may be considered "separate and distinct". The fire protection and life safety systems per 2021 IBC Chapter 9 shall be "scoped" (designed and engineered) accordingly based on the "separate and distinct" portions of the building.

Separate Sprinkler, Standpipe Risers "Combined"?

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