Lets look at this from the practical application side of things. The standpipe and its valves are there for the fire service, solely and only. Every department has its own operational standards, due in part to the hose nozzles they choose. Some want the hose valves at intermediate landings, some want them on the floor landing. Some want 100 psi, while others want 125 psi at the hose valve (because there is about 29 psi appliance loss in 100 ft of hose) and they want 100 psi at the nozzle.
Here on earth, the pressure of elevation is the same for everyone: 0.433 psi per ft of elevation – that is unless you went to the University of Maryland, where its 0.434 psi per ft. 😉 Some departments want the FDC on the address side of the building, while others may want more than one FDC for a high rise that is built on an entire city block. Getting back to the point… NFPA 14 is a minimum standard for the design and installation of standpipes which will be used by the first responders – who should be the only one’s deciding the design criteria and the location of equipment to be used in fighting fires. That’s my 2 cents – I hope that helps. bc *Bob Caputo, CFPS* *President* *American Fire Sprinkler Association* c: 760-908-7753 p: 214-349-5965 ext124 w: firesprinkler.org <https://www.facebook.com/firesprinkler.org/> <https://twitter.com/afsa/status/1039528345367732224> <https://www.linkedin.com/company/american-fire-sprinkler-association-afsa-/> <https://www.instagram.com/firesprinklerorg/> *Sprinkler Hydraulic Calculations Workshop* AFSA’s three-day, in-person workshop provides a deep dive into the principles of hydraulics, including the different types of pressure, calculating changes in pressure (elevation and friction loss), and node analysis. Click here <https://www.firesprinkler.org/programs/calculations/> for details and to register. *From:* Kyle.Montgomery <[email protected]> *Sent:* Wednesday, November 1, 2023 6:21 PM *To:* Discussion list on issues relating to automatic fire sprinklers < [email protected]> *Subject:* [Sprinklerforum] Re: [EXTERNAL] Re: Pressure Regulating Valves Residual Pressures Well, they can’t have a minimum of 100 psi AND a maximum of 100 psi available at the hose valve. So, if they want to limit the residual pressure to a maximum of 100 psi, then they need to deviate from NFPA 14 and allow LESS THAN 100 psi as the minimum. [Note: I suppose that maybe you could utilize a pilot-operated pressure-regulating valve at every hose valve location to keep the pressure right at 100 psi over a wide range of flow, but that would be unorthodox to say the least.] *Kyle Montgomery* *Aero Automatic Sprinkler Co.* *21605 N. Central Ave.* *Phoenix, AZ 85024* *Direct: 623.580.7820* *Cell: 602.763.4736* [email protected] *From:* Greg McGahan <[email protected]> *Sent:* Tuesday, October 31, 2023 9:16 AM *To:* Discussion list on issues relating to automatic fire sprinklers < [email protected]> *Subject:* [EXTERNAL] [Sprinklerforum] Re: Pressure Regulating Valves Residual Pressures With all due respect Rick, I have had Fire Departments very concerned about the residual pressure being greater than 100 psi for safety. Sizing PRV's is not the easiest part of a standpipe design. If you are in a jurisdiction that requires With all due respect Rick, I have had Fire Departments very concerned about the residual pressure being greater than 100 psi for safety. Sizing PRV's is not the easiest part of a standpipe design. If you are in a jurisdiction that requires flow testing and recording the pressures prior to the final inspection (as it should be per NFPA 14), guessing could cost a lot of money to correct. On Tue, Oct 31, 2023 at 10:49 AM Rick Matsuda <[email protected]> wrote: The requirements of NFPA-14 for the standpipe hose valves are maximum 175-psi static outlet pressure and minimum 100-psi residual outlet pressure while flowing 250-gpm through the hose valve. If your pump source is from the city mains, then make it easy on yourself and select a PRV hose valve that will provide maximum 165-psi static outlet pressure. This should allow you to use whatever residual inlet pressure while flowing the 750-gpm total standpipe demand and still provide the minimum 100-psi residual outlet pressure. I used the 165-psi static outlet pressure cause the pump inlet pressure may vary up/down which will vary the pump static outlet pressure which may raise the static outlet pressure over 175-psi. If the pump source has a constant pressure like an elevated tank, then select a PRV that will provide a maximum 175-psi outlet pressure. Just my opinion but if you select a PRV based on the maximum static outlet pressure then this should allow a bit more than the 100-psi minimum outlet pressure. Check the charts to verify this. Don’t select a PRV based on providing just the minimum outlet pressure. I think that the fire department will appreciate any extra pressure to offset the friction loss through their fire hoses. Rick Matsuda On Oct 31, 2023, at 7:24 AM, Eric Rieve <[email protected]> wrote: Micah, Looking at the spec sheet from Zurn I agree with Travis that you use your expected residual pressure while flowing the full system demand of 750gpm. I haven’t installed this valve myself, but you’ll notice on the residual pressure charts that the bonnet type curve lines stop well below 175psi. So, while you may pick a 120psi outlet pressure while flowing 750gpm, the extra play in the curve should allow the valve to maintain an outlet pressure below 175psi when being tested individually at 250gpm. Hope this helps! Eric Rieve, SET Rieve Fire Protection *From:* Micah Davis <[email protected]> *Sent:* Tuesday, October 31, 2023 6:53 AM *To:* SprinklerForum <[email protected]> *Subject:* [Sprinklerforum] Pressure Regulating Valves Residual Pressures Good morning, Forum! I hope everyone is having a great week!! I think I got this right, but someone is questioning me. I have an automatic standpipe with factory pressure-regulating valves (i.e., Zurn 4000). When calculating residual pressures at the inlet of the PRV to be used in the sizing charts, the question is, how much water should I be flowing in the system? One suggestion is only flowing 250 gpm at the hose valve you are sizing. The other suggestion is flowing the system demand flow per NFPA 14. In this case, that would be 750 gpm (250 gpm at each of the two most remote hose valves plus 250 gpm at the top of the only other standpipe). We are in agreement that the calculation should be a source calc to determine the actual pressure provided by the system. Thank you, Micah Davis Ferguson Fire Design _________________________________________________________ SprinklerForum mailing list: https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org <https://urldefense.com/v3/__https:/lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org__;!!Ba8_KKAT!Kd8DM2LZyWcEocYD3fg3JDRWY4EbJccNoJAO5nUwJLrU7pZ1PertiR4yFJWGSKkoUpznUXzAlJwSH_Xv107ezuPG$> To unsubscribe send an email to [email protected] _________________________________________________________ SprinklerForum mailing list: https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org <https://urldefense.com/v3/__https:/lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org__;!!Ba8_KKAT!Kd8DM2LZyWcEocYD3fg3JDRWY4EbJccNoJAO5nUwJLrU7pZ1PertiR4yFJWGSKkoUpznUXzAlJwSH_Xv107ezuPG$> To unsubscribe send an email to [email protected] -- Greg McGahan *Genesis Fire Services, LLC* *4912 Glover Lane. 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