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I have a project right now that the sprinkler system is being supplied from a tank and pump because the only water available is 25 gpm from a well. The AHJ refuses to allow NFPA 1142 for mobile apparatus to supply fire flow, saying it has to be a "fixed" system. However, he does let me use NFPA 1142 for fire flow rate.
I've added an additional 30,000 gallons to the tank for the 250 gpm fire flow for 2 hours. The AHJ just says to add a connection to the tank so the fire department can pull directly from the tank. The problem I'm running into is how can I be sure the fire department only uses 250 gpm so they don't rob the sprinkler system of any water? I don't have any experience doing this. Any advice or guidance you could provide would be greatly appreciated. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe
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Are sprinklers required in a noncombustible concealed space that contains combustible insulation?
I have a contractor who is trying to use polyurethane spray foam insulation in a noncombustible concealed space above a ceiling. It is an NFPA 13 system and they do not want to sprinkler it. To my knowledge, this spray foam insulation is combustible, and by filling a noncombustible space with it, it will need sprinklers. They are trying to propose intumescent paint, but I don't believe that changes anything for them. Do you all know of any applicable exceptions in this situation or if they don't need sprinklers? I think 9.2.1.13 is the only relevant section from 13, but I am having trouble finding whether this foam exceeds the 1,000BTU per square foot. Thank you. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe Is there an easy way for AHJ inspectors to tell the difference between a flexible coupling and a regular coupling?
Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I have been introduced to a project that involves six underground water storage tanks and an external pump house that will provide fire protection water to a fully sprinklered building.
We have been informed that the sprinkler contractor will be providing the building sprinkler system design, but not the underground storage tank portion of the project. The firm I work for performs a significant amount of fueling and convenience store design work for gas station and convenience store clients, but I am curious whether these water storage tank options are similar in nature to underground fuel storage tanks and their associated pumping equipment? Obviously, the medium is different (water versus fuel), but I am interested in understanding whether there are comparable design considerations, equipment types, or industry standards. Any guidance, resources, or lessons learned would be greatly appreciated. Thank you. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe A big thank you to our July contributors for another month of thoughtful questions, helpful answers, and shared expertise! We appreciate you!
A project we're looking at has a hydrant network that connects to fire sprinkler systems and hydrants.
What would be the process we'd need to consider for the water supply (fire pump and tank capacities)? How does the greatest sprinkler system demand (possibly with hose allowance) relate to the hydrant demand? Are they additive? Not all buildings could have sprinkler systems in the future, so we're questioning the relationship between sprinklered building system demands and the fire hydrant demand. Thanks for your input. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe When would we be permitted to remove a check valve from a zone control valve?
Like, what are the requirements for needing it one way or another? Thanks in advance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I have a CMDA wet system, protecting solid-piled Group A Plastics storage. The storage height will be under 12 feet.
Under Section 21.3.3(a), I have been led to the density of 0.60 gpm/sqft in Column C, over a remote area of 2,500 sqft. The 2,500 sqft remote area is what's getting me; it seems cut and dry that in my situation, I am stuck there unless I have a closed storage array. I wanted to verify against other people's interpretations: are there any other ways I am missing that would allow the area to be brought down to 2,000 sqft? I primarily ask because I have seen other systems in the field with areas of 2,000 with densities 0.40, 0.50, 0.60, and I'm unsure of how those systems have gotten to that point with the current codes. For clarity, I am using the 2022 edition of NFPA 13. Any input would be appreciated. Thanks. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe Does anyone know any background on the changes to Factory Mutual Data Sheet 8-9, Table 1?
The table used to use a set of formulas for all designs, which would apply a shape factor of 1.2 or 1.4 depending on ceiling construction/slope. It appears to have been updated in July of 2025, with changes being brought in that would allow 12 sprinkler designs to be calculated on the basis of 3 heads on 4 branch lines rather than using the old formulas, which, based on minimum spacing, was not possible for this to occur. There are no comments in the back or anything on FM’s website linked to testing that supports that change; any help would be appreciated. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe In an open, fully sprinklered building, can 50% of the floor area be protected by an automatic wet system, while the remaining 50% is protected by a pre-action system?
There is no wall separating the two areas. Thanks in advance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe A building will partially be a data center as part of a Group B Occupancy in the IBC.
Is a fire-resistance-rated separation required between the data halls and the offices? The data center area has accessory rooms such as a sprinkler riser room and a fiber cable entry, which are rated, but I'm looking at the data hall versus office specifically. Table 509 of the IBC doesn't mention anything about data center areas specifically. Thanks in advance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe Hi everyone, I have some questions regarding old high rise standpipes.
In many old high-rise buildings, they will have a wet standpipe fed from a gravity tank (or tanks), which is in turn filled by dedicated tank-fill pumps. Some will also have an additional manual fire pump down in the basement that can pressurize the standpipe upwards; I’m figuring just as backup for the existing roof tank reservoir. First question: Is this type of setup just a relic of the past since it’s just a manual backup pump? I haven’t found where in modern code it seems to be applicable to this whole setup. At least, it doesn’t seem to have any mention in NFPA 20, even though that’s the main fire pump book. Second question: All these vintage motors and controllers seem to be wound-rotor motors, and the controller is speed-controlled via resistor banks. Is the stepped speed control simply to reduce inrush by ramping one step at a time up to full speed, or are they intended to operate at reduced speeds on purpose? I’m figuring the modern equivalent to these old setups would likely be a soft-start controller if you’re just looking to reduce inrush, or a VFD controller if you want to run at reduced speeds on purpose. Of course, all of this conjecture is only if such a setup is even relevant to modern code. Thank you for any insight you can offer! Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe For an exposed exterior riser on a wet system, is insulation or mechanical protection required? If so, what type of insulation is best? This is in the Orlando, FL area. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe  I am working with a company storing Class IIIB liquids in plastic tanks. Tanks range in size from 2000, 3000, to 6100 gallons.
We struggled to find a design that works in NFPA and therefore went with a .40/3,000 from FM DS 7-32; however, now we do not know what to do with the containment requirements. What should the containment duration be? Since they are plastic tanks, I have assumed they would all fail and would essentially need containment around each tank? Thanks in advance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe We are designing foam system for an aircraft hangar in accordance with NFPA 409.
Is it acceptable to use AR-SFFF instead of AFFF with discharge density of 0.16 gpm/ft² (6.5 L/min/m²)? AR-SFFF is not specifically mentioned in NFPA 409. Thanks in advance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I wanted to get your thoughts on temporary fire pumps. We are in warm weather season here in MA, and a building wants to use a temporary fire pump to alleviate a fire detail that is on the building.
If this wasn't a high-rise, I honestly feel more inclined, but being that it is, I am more hesitant. I wanted to see if others have used them, and if so, what evidence did you bring to AHJs/Fire Depts? The client shopped around on their own accord and found an industrial end-suction centrifugal pump used for sewage bypass and general construction dewatering, which doesn't seem to be generally used for Fire Protection applications. Thanks in Advance! Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe There's an existing system in a warehouse with a pump. It's a grid system with an 8" main and 1" 17k ESFR sprinklers.
The main is in a 3' wide inaccessible "hallway". They added office space that will require 15 heads. There's a 4" floater main nearby. Can I connect to the 4" main to feed the added sprinklers? What do I need to consider in doing so? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I am designing a 25.2k ESFR system in warehouse with purlins set on tapered beams with about 8" wide flanges spaced 20' on center. The last beam in the project area runs 1'-5" off the wall creating a small beam pocket along the length of the wall. Current head spacing is 10'x10', and 18" below ceiling. The sprinklers adjacent to the beam are 3'-10" from centerline, or 5'-3" from the wall. This would require heads within the beam pocket, but the clearance between the wall and beam would obstruct sprinkler discharge. Are there any special exceptions that would allow heads to be omitted from the pocket? Or how could I approach this condition differently to meet code? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe    While NFPA 20 requires a minimum NEMA Type 2 enclosure for fire pump controllers, an alternative view has been expressed that a "NEMA Type 3R" enclosure should be provided where the fire pump room is sprinkler-protected.
The rationale is that activation of the sprinkler system during a fire event may subject the enclosure to water spray similar to rain exposure, for which NEMA Type 3R enclosures are designed to provide protection. What is your thought on this? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I have a retrofit application where the sprinkler system needs to be supported from Pyro-Bloc, as that is what is making up the structure of the floor above. NFPA-13 (2022) does not allow the use of toggles (that's what the plumbers and mechanical contractors are using), and the material is too brittle to use drop-ins or expanding anchors.
Any recommendations on how to support the piping? This is specifically 2" and larger. Thanks in advance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe When calculating manual standpipe systems per NFPA 14, are there any tips on calculating upstream from the FDC back through the hose lay back to the apparatus?
And I assume even considering the underground supply the apparatus is drawing from? I know many pumper trucks are rated at 1,500 gpm at 150 psi, but I assume one would need to verify that, and what length, diameter, and type of hose they utilize from the truck to the FDC. I see too many calcs that assume an "infinite" water supply if it is supplied by a pumper truck. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe Have a question on whether or not thrust blocks are required for heat-fused connections.
Per Section 10.6.3 of NFPA 24, additional restraints are not required for heat-fused connections. Under PPI Chapter 7, for pressure piping systems that are joined by heat fusion, flanges are fully restrained and do not require external joint restraints or thrust blocks. For the above case, is a pressure thrust block required? We will use a concrete pad underneath the hydrant and PIV, but not a pressure thrust block. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe Is there any relevant code or standard that restricts the use of flexible sprinkler armovers above hard ceilings?
Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe An existing building needs to replace its fire alarm system because the current system cannot support elevator recall, which is required for the new elevator they need to install. In Massachusetts, the IEBC states that when a fire alarm system is replaced, heat detectors will be installed if the building is not fully sprinklered. Should the building include providing low-frequency sounders inside the units to ensure adequate audibility at the pillow? I have heard mixed interpretations from other AHJs. The attachment shows the code citation. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe  In a highrise building with a sprinkler system designed under NFPA 13, are above-ceiling smoke detectors required?
There are limited combustible materials (wiring, steel pipe, steel ductwork) and in other areas PVC pipe. Are smoke detectors required for the above ceiling spaces? Should they be considered if not? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe |
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