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I have a campus housing situation with a few thousand reliable 3.9k heads that are no longer made, on 16x16 spacing, requiring 17 gpm and 19 psi per the cut sheet.
We are looking to replace these with 4.2k sprinklers, same 16x16 spacing, is 16 gpm and 14.5 psi per the cut sheet. Question is, I know the 4.2K falls just over the allowed 5% deviation, but these 4.2k sprinklers are more "efficient", so would they require running new hydraulic calcs to verify, or would it be safe to swap out as is? Thank you in advance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe
8 Comments
Has anyone encountered unusually high and consistent static pressures in sprinkler systems where there is no visible fire pump?
I recently came across two examples that raised questions: - A riser in our major metro showing about 165 psi static pressure. - A five-story hotel with roughly 125 psi static pressure on every level, consistently throughout the building. In both cases, I searched extensively for a fire pump and could not find one. The buildings were on normal city water supplies, not private systems or campuses, and there was nothing obviously unusual about the sites. It made me wonder whether there are situations where some type of booster pump is being used for sprinkler systems without being readily identified as a traditional NFPA 20 fire pump? Or perhaps there is another explanation entirely. Has anyone else seen this? If so: - What was the situation? - Was there hidden pressure-boosting equipment involved? - Are there municipalities or systems where this is more common? - Or is there another explanation for maintaining these pressures throughout a building without a fire pump? Interested to hear what others have encountered. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe Is there a minimum height requirement of pipes in an underground parking garage?
Is that different than an ordinary occupiable space? My vehicle is 75.8 inches tall, for instance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I have a DoW project with specifications that require the diesel fire pump flow meter to discharge both into the pump suction and through the test header. I don't have experience with this setup; in all my previous projects, the diesel fire pump discharged back to the water tank as well as to the test header. I understand that NFPA 20 allows this arrangement (see attached figure from the 2025 edition), but I'm curious how it works in practice for two main reasons: 1. If we close the tank valve during testing, the pump's suction pipe will receive considerable pressure. Will this repeated pressure adjustment after each test impact the longevity of the soft packing, particularly regarding increased water leakage? 2. How does a diesel fire pump cool its motor if the heat exchanger water isn't returned to the tank with fresh cool water coming in? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe  Do you have to protect the whole attic that has smoke partitions with fire sprinklers if only one area has gas-fueled equipment in it? Can you just protect the one area that has the fuel-fired equipment in it? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe  We have a coffered ceiling with a 3" drop as per design, and we'd like to have the fire sprinkler drop down 3" automatically when activated.
Is there a product or technique that can be used for this? It's a high-end commercial space. Thanks in advance. Moderator's Note: Updated "Chauffeured" to "Coffered." Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I am working on a new building in a rural area that will require sprinkler protection. There is no access to a public water supply, only a 30-100 gpm well on site.
Options for fire suppression water include pumping from a large farm pond 150 feet away or installing a 15,000-gallon water storage tank with a pump. Any thoughts on which option is more feasible and cost-effective, or any alternatives we're not considering? This is in a freezing climate. Thank you in advance! Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I've got a high-rise project in a seismic zone higher than category C. We are required by IBC to have a secondary water supply other than the city supply (IBC 403.3.3). The structural team is pushing to not put the tank on the roof, and our site is extremely limited, so there is discussion about trying to bury the tank.
What pump/tank configurations are available for this situation? I am aware of either a concrete or fiberglass tank with a vertical turbine pump, but can you tie in the city supply to a vertical turbine submerged in a tank? Is there a way to appease this rule other than a secondary fire tank that I'm not thinking of? Thank you in advance for any help. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe There is a great debate in my office whether or not we are required to protect to the back of lower/upper cabinets.
NFPA 13 9.2.9.3 (2022) states that we need to cover the area below the cabinets to the back wall. Seems pretty straightforward to me, but someone in my office states that we only sprinkler floor space, without providing any code reference. Do we protect to the wall, or the face of the cabinet where only floor area is exposed? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe When hose allowance is added to the sprinkler demand on a Class III Standpipe/Sprinkler wet riser, where on the system are the inside and outside flow and pressure allowances input when calculating the system?
NFPA 13 Chapter 19 states that the allowances are not required when calculating a combined system, which appears to contradict NFPA 14 requirements to include them. In my case, the sprinkler demand is for OH2 (ceiling higher than 40 ft), resulting in a sprinkler demand plus hose allowance that is greater than the standpipe demand. If I don’t include hose allowance in the sprinkler calculation as per Chapter 19, this combined system is not equivalent and robust as two independent systems. Any thoughts? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe Is sprinkler protection required for the overhang shown in the simplified detail below? If sprinkler protection IS NOT required, which allowable sprinkler omission does this comply with in NFPA 13 (2022)? If sprinkler protection IS required, what component(s) are triggering this requirement? Thank you! Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe  We have a high-rise building (residential from 5-24 floors).
Can CPVC listed piping be utilized in high‑rise fire sprinkler systems (residential portion), and are there restrictions related to maximum elevation and/or pressure limitations? Thanks in advance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe Under NFPA 13, 2022: in noncombustible stair shafts, can sprinklers be omitted at the entire bottom area of the stairs?
For example, if the first floor is the bottom of the stairs, can sprinklers be omitted under the second floor at the area where you enter the stairwell? Section 9.3.4.2.3.1 states, "Sprinklers shall be permitted to be omitted from the bottom of the stairwell when the space under the stairs at the bottom is blocked off so that no storage can occur." Is this only referring to under the intermediate landing and not the entire first floor area of the stairs? I know that at the beginning of this Section 9.3.4.2.1 states in part "under the first accessible landing above the bottom of the shaft." So does the omission apply in this case? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe Would ESFR K25.2 be permitted to be installed on a single interlock pre-action system?
I have a system conversion that is currently a gridded warehouse with K25.2 ESFR pendents that the client wants to convert to single interlock. The system will be converted to not be gridded anymore, but I am not seeing any clear information on whether the existing ESFR can remain. If we were to remove the sprinklers, it would now dive into possible in-racks to protect the class IV storage. Warehouse is 35ft max height, bar joist. Thanks in advance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe We have a situation where we need to replace a 40-year-old fire pump where the original RPZ is located downstream of the pump. Our current code requires all BFP's upstream of the pump. We are worried that the RPZ will start dumping every time the pump is started.
Does anyone have experience with this that could lend a recommendation? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe For a dental office, is a sprinkler required in the gas storage closet (nitrous oxide and oxygen) on the main floor?
The basement is sprinklered, but the main floor is not. If sprinklers are required, can the system be tied into the existing basement sprinkler system? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I have 6" and 8" sprinkler pipes that need to be supported by pipe stands at 26 ft.
What does NFPA 13 require to be done/designed for this situation? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe As an AHJ, how do we respond to someone that wants to use new technology that is not recognized by Code / Standard?
Such as Sonic Fire Tech? https://www.sonicfiretech.com/ Do we recognize it or require UL / FM / "Approval" before allowing it as an approved system? In other words, what would be the basis for saying "no" at this stage? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I am doing CMDA overhead sprinklers for in-rack class 4 storage at 15' - a new system.
As I was navigating through NFPA 13 2022 Chapter 21, I came to 21.4, which seems to be where I should be. My question is: 21.4.1.1.1 is where you start, which states that if it's a new sprinkler system, the demand shall be determined in accordance with 24.4.1.2.2.1. BUT, I skipped that and went on to 21.4.1.2.1.1, which seems to be for the EXACT SAME CRITERIA (unless I cannot read/comprehend, which is possible)! So when would you use 24.4.1.2.2.1 over 21.4.1.2.1.1? When we use 24.4.1.2.2.1 with the modification chart, we get a density of 0.297, and when we use 24.4.1.2.1.1, it calls for 0.30. So they're pretty much the same... but I'm not seeing why you would ever use 24.4.1.2.1.1 since 24.4.1.1.1 directs you to 24.4.1.2.2.1 and bypasses the other. Hopefully, this makes sense. --- 21.4.1.1 General 21.4.1.1.1 Ceiling sprinkler water demand for new systems shall be determined in accordance with 21.4.1.2.2.1 for single and double row racks or... 21.4.1.1.2 Ceiling sprinkler water demand for the modification of existing systems... 21.4.1.2 Protection Criteria for Single or Double-Row Rack Storage of Class I-IV Commodities over 12 ft Up to and Including 25 ft in Height. 21.4.1.2.1 New Systems Criteria for Single- or Double-Row Rack Storage of Class I-IV Commodities Stored Over 12 ft Up to and Including 25 ft in Height. 21.4.1.2.1.1 For single- or double-row racks for Class I, II, III, or IV commodities, encapsulated or nonencapsulated, the ceiling sprinkler demand.... shall be selected from the criteria in Table 21.4.1.2.1.1(a) through Table 21.4.1.2.1.1(c) that are appropriate for... and shall be modified as appropriate by 21.4.1.4. --- Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe In a four-story educational building, we have a large pipe chase that wraps around the men’s and women’s restrooms on each floor. The highlighted area in the attached sketch is the pipe chase area.  The wall on the left (with the red arrows pointing at it) is a 1 hour rated shaft wall. All the other walls around the pipe chase are non-rated wall assemblies. There are doors (blue boxes) giving access to this area in three different locations. There isn’t any equipment or sources of ignition located inside the chase, just plumbing pipe.
While the area is not to be used for storage, we are concerned that the presence of the doors will allow people to do so. The Architect/Engineer has directed us not to protect this area with sprinklers. Are sprinklers required inside this chase or can they be omitted as directed by the A/E? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I have a plan reviewer requiring calculations (CFH) for a diesel fuel tank because the vent extends further than the UL label is calculated for.
What are the guidelines and how is this calculation performed? The comment: "Provide the required emergency vent capacity, in Cubic Feet Per Hour (CFH), for the primary and secondary fuel tank emergency vents. The venting capacity should be indicated on the UL label on fuel tank. The shop drawings don't list the emergency vent capacity. Note: The capacity listed on the UL label is calculated with the vent within 12 inches of the tank body. If the vent is extended above the tank more than 12-inches, additional calculations are required to account for the additional piping and height above the fuel tank. These calculations are required to be computed by a registered engineer." Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe NFPA 14 requires PRV redundancy when more than two hose connections are supplied downstream of a PRV.
Does NFPA 13 have a similar requirement for sprinkler systems, or can multiple sprinkler systems be controlled by a single PRV? We are proposing to feed a riser manifold controlling (6) sprinkler systems to be supplied by a single ORV without a redundant loop. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe NFPA 13 Section 16.2.4 concerning protective coverings for sprinklers only references spray booths and mixing rooms.
I have a building that produces particulates in the air (a chip and tortilla factory). The concern is that we replace these sprinklers, and they will quickly need to be replaced again in a couple of years (96 total). I want to put on cellophane bags to protect them. The existing sprinklers are standard response. I plan to go to the AHJ for their approval, but I wanted to get the opinion of others who may have experienced something like this. Thank you in advance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe Can a fire pump test report be used in place of a hydrant flow test?
For an existing building, a fire pump flow test has to be done annually. It should include all the information a hydrant flow test provides to perform a hydraulic calculation for an existing building modification. Is there any code basis for taking this approach? I have an AHJ that keeps pushing back on this approach for determining the water supply information. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe Is a water storage tank for an NFPA 13 system required to be UL listed, or does it need to simply be NFPA 22 compliant?
I was always taught that a tank had to be at least UL Listed for fire protection, but I have a supplier telling me otherwise, and the price he offers is less than half that of a UL/FM tank. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe |
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