Use 65 or 100 psi for Manual Class III Standpipe?

9/26/2023

What is the required pressure for a manual Class III standpipe, 65 or 100 psi?

We're working on a 44'-4" high, 5-story, Type V-B construction building that has a 1-story garage and amenities. The upper floor is R-2.

The local code says I can have Class III standpipe. As I go through NFPA 13 and NFPA 14, it circles back around to 2-1/2" outlets, except with 2-1/2" x 1-1/2" reducers and caps.

It's going to be fully-sprinklered with a combination standpipe in one stairwell, and just one standpipe riser in the other.

Does this sound correct given the project?

Thanks in advance.

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6 Comments

Dan Wilder

9/26/2023 08:14:45 am

IFC 2021 - 905.3.1 requires the Class III based on your description (4 or more stories above grade, Floor level on highest story is greater than 30' above lowest level of FD access), but allows Class I in fully sprinklered buildings when the hose lines will not be used by trained personnel or the FD (905.3.1 Exception 5). Any reference to standpipes out of this section references to NFPA 14 (905.2). Als, doesn't account for any local AHJ adoptions or modifications...

As to the requirements NFPA 14-19'....
Class III - 5.3.3.2 allows use of Class I connections with reducing caps (2½" ->1½" and by FD approval) in lieu of the Class II connections.

5.4.2.1 allows for manual wet for Class I only, the Class III connections shall be automatic but 7.7.1 allows for manual supply means

7.8.1 & 7.10.1.1 requires 250GPM @ 100 PSI (via the manual wet design allowance)
7.8.1 & 7.10.2.1.1 requires 100GPM @ 65 PSI (via an automatic water source) but the maximum residual pressure shall not exceed 100PSI (7.2.3.1) but does not apply to locations with reducing caps and/or when there is no hose provided (7.2.3.1.1 & 7.2.3.1.2)

Both of these requirements are "through" the valve, not to it....Using MFG data of Table 8.3.1.3

So, for this application as described I would use -
Manual wet calculation for 750 GPM @ 100PSI from 3 hose valves (2 HV on hydraulically remote standpipe, 1 HV on the 2nd standpipe)
Manual wet calculation for 100GPM @ 65PSI from 1 hose valve (hydraulically remote)

As I don't deal with Class III connections (none of my AHJ's allow them), there may be some exceptions I am missing so looking to get some education from the group.

Unsure on any requirements for use of the 1½" connections when the FDC is pumping into the system to make the 2½" valves work (active vs cleanup operations) for pressure reductions...I'd assume it's 2 separate operations and would not overlap on requirements.

NFPA 13 hose valves do not play into this design based on the IFC requirements.

https://www.sprinklerage.com/standpipe-systems-design-installation-requirements/

Danial Bartle

9/26/2023 09:53:42 am

Speaking as a retired firefighter, the "high-rise" hose packs usually have 1 1/2 or 1 3/4 hose preconnected to a nozzle, and a 2 1/2 x 1 1/2 (2) gated wye. The wye is connected to the standpipe and one line is used with the ability to add another 1 1/2 connection without stopping water flow. So generally up to 2 handlines per 2 1/12 connection.

kimberly olivas

10/2/2023 09:48:50 am

Thank you!

Glenn Berger

9/26/2023 08:39:57 am

Agree with Dan's responses above.

You do need to verify that the owner/occupant wants a Class III standpipe. Recommend only providing Class I standpipes (hose valves / outlets - no hoses), unless instructed otherwise.

Jesse

9/26/2023 08:46:06 am

Agree with both Dan and Glenn. And yourcalc is 250-gpm @ 100-psis.

Casey Milhorn

9/26/2023 10:01:49 am

I agree with the responses and that a Class I standpipe, using Class III connections, is the most common method for standpipe design and install that I see (for non-high rise buildings). As Dan said, definitely talk to your local AHJ for any variances they have/want.

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Use 65 or 100 psi for Manual Class III Standpipe?

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