If your standpipe is manual then you hand to account for the FDC pressure I believe
Benjamin Young On Thu, Sep 24, 2026 at 10:45 AM Joe Burtell [MT-BILL] < [email protected]> wrote: > I've got a combined sprinkler/standpipe system I'm working through and > want to bounce a question off you, since you're on the NFPA 14 committee. > > THE SCENARIO > > I'm using NFPA 13 (2019) and NFPA 14 (2019). Facts: > > The FDC will be supplied with a pumper truck at 200 psi, as this is a > manual standpipe system. > All pipe, fittings, and valves on the combined riser are rated 300 psi or > greater. > The sprinklers are residential sprinklers, which only come rated to 175 > psi max — there's no higher-pressure listed option to spec around this. > > Since the riser is shared between the standpipe and sprinkler systems, I'm > trying to nail down whether that 200 psi FDC-boosted pressure is something > the sprinkler branch has to be designed/protected against, or whether it's > legitimately excluded from that side. > > THE DEFINITION CONFLICT > > NFPA 13 (2019), 3.3.235 - System Working Pressure: > "The maximum anticipated static (nonflowing) or flowing pressure applied > to sprinkler system components exclusive of surge pressures and exclusive > of pressure from the fire department connection." > > NFPA 14 (2019), 3.3.24 - System Working Pressure: > "The maximum anticipated static (nonflowing) or flowing pressure applied > to standpipe system components exclusive of surge pressures." > > NFPA 14's 2019 definition dropped the FDC exclusion that NFPA 13 still > carries. My understanding is the 2016 edition of NFPA 14 did exclude FDC > pressure, and the exclusion came back (worded differently, as an explicit > inclusion this time) in the 2024 rewrite. So in the 2019 pairing I'm stuck > with, NFPA 13 excludes FDC pressure from working pressure, and NFPA 14 > doesn't carve it back out. > > WHY IT MATTERS HERE > > NFPA 13 also requires sprinkler components to be rated for at least 175 > psi or the max pressure they're actually exposed to, whichever is greater — > separate from how "system working pressure" is defined as a term. On a > shared riser, if the standpipe side gets boosted to 200 psi via the FDC, > that pressure is physically present at the riser regardless of which > standard's definition "counts" it. > > My residential sprinklers are only rated to 175 psi with no higher-rated > alternative. If any part of the sprinkler branch could see more than 175 > psi — even from FDC boost — that looks like a rating gap unless a PRV goes > in on the sprinkler side of the floor control assembly. > > WHAT I'D LOVE YOUR READ ON > > In the 2019 edition pairing, is FDC-boosted pressure meant to count as > part of the standpipe's "system working pressure," given NFPA 14 (2019) > dropped the exclusion language that NFPA 13 (still) has? > For a combined system on a shared riser, does NFPA 13's exclusion of FDC > pressure actually relieve the sprinkler branch from needing protection > against it — or does the "rated for what it's exposed to" requirement > override that once the riser is shared? > Practically: with 200 psi possible at the riser and 175 psi-max > residential sprinklers with no higher-rated option, is a PRV at the > sprinkler takeoff mandatory wherever calculated pressure (inclusive of > anticipated FDC contribution) could exceed 175 psi? Or is there some other > intended mechanism — FDC placard limits, a different assumption about how > the two pressures interact on a shared riser — that I'm missing? > > Any insight into the intent behind the 2019 language change, and how it's > supposed to interact with NFPA 13's exclusion in a combined system, would > really help. > > > Joe Burtell > Design Manager > D > C > > > 406-204-4653 > 406-861-4507 > 3004 > <https://www.google.com/maps/search/3004+1st+Ave+South+Billings+,+MT+59101+Office:+406?entry=gmail&source=g> > 1st > <https://www.google.com/maps/search/3004+1st+Ave+South+Billings+,+MT+59101+Office:+406?entry=gmail&source=g> > Ave > <https://www.google.com/maps/search/3004+1st+Ave+South+Billings+,+MT+59101+Office:+406?entry=gmail&source=g> > South > <https://www.google.com/maps/search/3004+1st+Ave+South+Billings+,+MT+59101+Office:+406?entry=gmail&source=g> > Billings > <https://www.google.com/maps/search/3004+1st+Ave+South+Billings+,+MT+59101+Office:+406?entry=gmail&source=g> > , > MT > 59101 > <https://www.google.com/maps/search/3004+1st+Ave+South+Billings+,+MT+59101+Office:+406?entry=gmail&source=g> > Office: > <https://www.google.com/maps/search/3004+1st+Ave+South+Billings+,+MT+59101+Office:+406?entry=gmail&source=g> > > 406‑247‑0470 > www.summitfiresecurity.com > This is a commercial email sent by Summit Companies or one of its > affiliates, > <https://www.google.com/maps/search/3004+1st+Ave+South+Billings+,+MT+59101+Office:+406?entry=gmail&source=g> > with an office located at 1250 Northland Drive, Suite 200, Mendota > Heights, MN 55120 > <https://www.google.com/maps/search/1250+Northland+Drive,+Suite+200,+Mendota+Heights,+MN+55120?entry=gmail&source=g>. > If you no longer wish to receive commercial emails from Summit Companies, > please let us know by contacting us by mail or by email at > privacy@summitcompanies to opt out. > > IMPORTANT: Information contained in this e-mail may be privileged, > confidential, and subject to other protections, including, but not limited > to, the Electronic Communications Privacy Act, 18 U.S.C. 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