NFPA 13 2025 still includes the “exclusive of pressure from the FDC” so it’s made it through a couple of editions…
*noting the horizontal “A” bar joist obstruction dimension was there for 20 years or so. From a performance standpoint, (quite a few years now) of installing, flow testing and commissioning manual standpipe systems, I’ve never had an issue with intermittent sprinkler system side pressures over 200 psi on combined systems. Infact, We regularly hydro test to 250 psi based on previous experience of 200 psi not indicating leaks. I’m sure anyone in the VA area knows the jurisdiction we found this out in. Ultimately, my take is if your working pressure is 175 psi, and you hydro a system at 225 psi, 225 psi is not the working pressure, 175 psi is still the working pressure, but the system is capable of accepting intermittent higher test pressures. If a manual wet standpipe requires 200 psi, but the supply pressure is 175 psi, 200 psi is the working pressure, provided that in order to work as designed the system requires 200 psi. When the same FDC is connected to the sprinkler system, 175 is still the working pressure, and the standard accommodated for that in the verbiage. Jamie Seidl SET # 107472 Century Fire Protection<http://www.centuryfp.com/> | General Manager 3600 Woodpark Blvd. Suite G, Charlotte, NC 28206 p 704 888 3473 | m 704 650 0033 <https://www.facebook.com/CenturyFP> [cid:[email protected]] <https://www.linkedin.com/company/century-fire-protection> [cid:[email protected]] <https://www.instagram.com/centuryfp/> From: Steve Leyton <[email protected]> Sent: Thursday, September 24, 2026 2:34 PM To: Discussion list on issues relating to automatic fire sprinklers <[email protected]> Subject: [Sprinklerforum] Re: Quick question on NFPA 13/14 "System Working Pressure" and FDC-boosted pressure in a combined system External Email: ONLY open links/attachments from known safe sources That language has been updated, at least in 14, so check the applicable editions of the standards. From: Jamie Seidl <[email protected]<mailto:[email protected]>> Sent: Thursday, September 24, 2026 11:31 AM To: Discussion list on issues relating to automatic fire sprinklers <[email protected]<mailto:[email protected]>> Subject: [Sprinklerforum] Re: Quick question on NFPA 13/14 "System Working Pressure" and FDC-boosted pressure in a combined system My read is, the boost pressure variable from the FDC is to be excluded. This is the NFPA 13 portion of the system, and governed under such, so 3.3.235 applies. The difference here is the standpipe system. Where the committee dropped the "exclusive of pressure from the fire department connection". On the vast majority of Standpipe systems, (manual) the FDC becomes the system working pressure due to the FDC supplying the system. I'd also imagine they didn't think it would be much of an issue since generally all of the standpipe components are rated to 300 psi. Jamie Seidl On Thu, Sep 24, 2026 at 10:45 AM Joe Burtell [MT-BILL] <[email protected]<mailto:[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. 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