Hose Allowance & Single Waterflow in NFPA 13R?

10/7/2019

I have been asked to design a sprinkler system for a 4 story building as per NFPA 13R. The building has existing standpipes consisting of three 2 1/2” risers. I am hoping to use the existing standpipe risers to also feed the sprinkler system.

In this scenario would it make sense to include a hose allowance even though NFPA 13R does not require it? Also, since NFPA 13R doesn’t require zoning by floor, would it be plausible to have one single “Standpipe & Sprinkler Water Flow Alarm” at the water entry?

I appreciate and respect your input.

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3 Comments

Joe

10/7/2019 04:55:42 pm

One waterflow should be OK, as long as the total square footage for all floor levels doesn't exceed the limits of a single system.

NFPA 13 requires floor control valves for buildings over 2 stories but even as a more stringent standard allows a single control valve, check valve, main drain and flow switch when the total area protected doesn't exceed the NFPA 13 limits (see NFPA 13-2016 8.2.4.3). For light and ordinary hazard it's 52,000 sqft.

sean

10/8/2019 06:52:52 am

NFPA 14 requires sprinkler/standpipe combination risers to be equipped with certain features.

NFPA 13R does require hose allowance it is calculated by the number of plumbing fixtures.

Skyler

10/9/2019 12:32:08 pm

First, I really like the idea of adding hose demand. Knowing that the intent of 13R is that the local fire department will be needed to knock down a fire. That being said, I don't know what your city supply is like, but 2-1/2" standpipes are unlikely to support 100 GPM and the flow from 4 residential sprinklers. I would try it, and if I could get it to work with the hose demand, then great. Otherwise, you can hang your hat on the fact that there is no code requirement for hose demand in 13R and this is probably a manual standpipe; the fire department can/will pump their own water when they use the standpipe. City pressure around here isn't good enough by itself to get the roughly 80 psi that our firemen's fog nozzles want anyway.

I would do one flow switch if it was me. You would be meeting 13R requirements. I have had a fire marshall tell me that "I'm not sending my men in to a building where they don't know if the fire is on the first or second floor first". I tried to explain that there is no code basis for this requirement of his and that the floors were only 12,000 square foot each, meaning they would have a tougher time finding it in a 52,000 square foot single story building. Ultimately, I ate the cost to run an entire other level of piping (rather than up the walls connected to the first floor), just so I didn't make him angry for the other 12 systems we had to install that did not have this issue. Now I call the local fire department BEFORE I bid jobs where I don't have each floor zoned. Perhaps this would be a good idea for you as well.

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