Standpipe for Scissor Stair Need 500 or 750 gpm?

11/19/2025

For scissor stairs having 2 separate standpipe risers (one of them is a combined sprinkler and standpipe system) running 12 floors, how do we size the pump flow rate required?

Can we argue that we can use a 500GPM pump since the Risers are in close proximity to each other and are within one stairwell, or should we use a 750GPM pump following the NFPA 14 sizing of 500GPM plus 250 GPM per additional riser?

Thanks in advance.

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4 Comments

Anthony

11/19/2025 08:01:34 am

NFPA 14- 2024 ed
9.3 Number of Standpipes.
9.3.2 Scissor Stairs.

Where scissor stairs are provided, separate standpipes shall be provided for each stair within the exit enclosure(s).

I think code requires it as its under the header is 'number of standpipes'. So you'll need to prove 750 at that stair well, the opportunity for both standpipes to be used is too high. Though in the same shaft I would argue its an adjacent required exit. I think hose travel may vary as well depending on the stair arrangement.

Other thoughts:

The difference from 500 to 750 will have some cost but will depend on the HP change. Could impact the generator costs here for the electrical load, assuming you 're using an electrical pump.

At 12 stories you'll need PRVs. I think this is a good example of where a prv station is going to be more advantageous than individual floor level units.

Anthony

11/19/2025 08:02:31 am

Good article to reference: https://nfsa.org/2024/03/15/scissor-stairs-and-egress/

Glenn Berger

11/19/2025 08:24:15 am

One stairwell (stair enclosure) for a building with 12 floors???

As far as standpipe design is concern - you need to follow NFPA 14, if that standard is applicable to the building.

Jack G

11/19/2025 10:16:03 am

They are to be considered as 2 standpipes so 500 for the first plus 250 gpm for the second And 250 for additional up ton1000 gpm applies.
Under some applications they are considered 2 separate egresses but placed together to save space.
Under NFPA guidelines each stair must be separate with fire rated construction and smoke so that if one stair is compromised it does not compromise both.
The IBC considers sisscor stairs as 1 exit way not 2 , meaning they don’t fufull the requirements for additional separate exits in tall buildings Unless thet are separated by fire and smoke rated construction ( indicated above) .
In my opinion,since they have access to Alternate floors ( discharge-2-4-6-8-10-12; and discharge - 1-3-5-7-9-11)
They do not provide 2 means of egress for each floor so another stair should be provided.

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Standpipe for Scissor Stair Need 500 or 750 gpm?

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