True, if your tank is down for maintenance… That occurs pretty infrequently, I’m sure we all agree. Like maybe once every 20 years or so? We take sprinkler systems in and out of service without any special consideration all the time and keep in mind that there are options for fire watch, temporary piping arrangements and the FDC to help mitigate impairment for the short period of time that the tank might have to be emptied.
The foregoing is my opinion only and does not represent NFPA or the NFPA 14 Technical Committee, nor intended to serve as an interpretation of the standard. Protection Design and Consulting Steve Leyton, President T | 619.255.8964 x 102 | www.protectiondesign.com<http://www.protectiondesign.com/> 2851 Camino Del Rio South | Suite 210 | San Diego, CA 92108 Fire Protection System Design | Consulting | Planning | Training From: Travis Mack <t.m...@mepcad.com> Sent: Monday, September 25, 2023 12:11 PM To: Discussion list on issues relating to automatic fire sprinklers <sprinklerforum@lists.firesprinkler.org> Subject: [Sprinklerforum] Re: Standpipe PRV Question Steve: I was envisioning that you had your city supply going to the tank and you had the full tank. So if there is activation, you have either city supply or tank as back up. That is no issue. But if there is no direct bypass around the tank, then when your tank is down for maintenance, your entire water supply is down for that period. Maybe I am not perfectly picturing what you are indicating. Travis Mack, SET M.E.P.CAD | Instructor / Support 181 N. Arroyo Grande Blvd. #105 I Henderson, NV 89074 www.mepcad.com<http://www.mepcad.com/> | m: 480.547.9348| Whatspp: +14805479348 Email: t.m...@mepcad.com<mailto:t.m...@mepcad.com> AutoSPRINK | AutoSPRINK FAB | AutoSPRINK RVT | AlarmCAD From: Steve Leyton <st...@protectiondesign.com<mailto:st...@protectiondesign.com>> Sent: Monday, September 25, 2023 12:05 PM To: Discussion list on issues relating to automatic fire sprinklers <sprinklerforum@lists.firesprinkler.org<mailto:sprinklerforum@lists.firesprinkler.org>> Subject: [Sprinklerforum] Re: Standpipe PRV Question Respectfully don’t concur. The point of the tank is to store a reserve of standpipe water or sprinkler water, whichever volume is highest given demand x duration. This requirement is intended to mitigate interruption of the primary water supply (city main) due to a cataclysmic seismic event that might damage the service lateral or public system. Assuming it’s sized correctly, you start with a full tank and the pump begins drafting and almost immediately, the autofill opens. We use 6” fill lines, so once its open, the fill line will either maintain the tank level or augment it. If at some point the supply to the tank is interrupted, you at least have tank water for the calculated duration at full demand. Even if the public (fill) supply is interrupted before the pump operates, you still have a full tank at the start. Which is the point, to assure an adequate water supply for the duration of an activation. Not two separate (and potentially concurrent) water supplies, just a back-up to assure that you have one reliable one. And you won’t have that if you’re drafting just from the city main and it gets interrupted, so I think this arrangement is consistent with the intent. And all the AHJ’s out here in Earthquake Country seem to agree, as this is a fairly standard arrangement. The foregoing is my opinion only and does not represent NFPA or the NFPA 14 Technical Committee, nor intended to serve as an interpretation of the standard. Protection Design and Consulting Steve Leyton, President T | 619.255.8964 x 102 | www.protectiondesign.com<http://www.protectiondesign.com/> 2851 Camino Del Rio South | Suite 210 | San Diego, CA 92108 Fire Protection System Design | Consulting | Planning | Training From: Travis Mack <t.m...@mepcad.com<mailto:t.m...@mepcad.com>> Sent: Monday, September 25, 2023 9:47 AM To: Discussion list on issues relating to automatic fire sprinklers <sprinklerforum@lists.firesprinkler.org<mailto:sprinklerforum@lists.firesprinkler.org>> Subject: [Sprinklerforum] Re: Standpipe PRV Question In my opinion, that is not dual water supplies. If the tank is down your water supply is down. You need one connected to the city and one connected to the tank. Yes. It can be quite tough to balance that calc. I’ve had to put a PRV on the incoming line so as to basically kill most of the supply pressure. Travis Mack, SET M.E.P.CAD | 181 N. Arroyo Grande Blvd. #105 I Henderson, NV 89074 www.mepcad.com<http://www.mepcad.com/> | m: 480.547.9348 AutoSPRINK | AutoSPRINK FAB | AutoSPRINK RVT | AlarmCAD Book appointment time in my calendar https://calendly.com/t_mack_mepcad ________________________________ From: Micah Davis <micah...@gmail.com<mailto:micah...@gmail.com>> Sent: Monday, September 25, 2023 9:17:40 AM To: Discussion list on issues relating to automatic fire sprinklers <sprinklerforum@lists.firesprinkler.org<mailto:sprinklerforum@lists.firesprinkler.org>> Subject: [Sprinklerforum] Re: Standpipe PRV Question Thank you for the response, Steve! Does the redundant fill valves for the tank satisfy the secondary supply requirement of the IBC without an additional tank? I was interpreting the city main connected to the pump as the primary supply and the tank as the secondary supply (or vice versa). If my interpretation is wrong and the tank with redundant fill valves meets BOTH the primary and secondary water supply requirements, I can NOT connect the city water main to the fire pump, and the problem is solved using your method above. Am I tracking correctly? My thought is that if the city main stays connected to the pump and my demand calcs and PRV settings are based on the supply from the tank (which I think is correct), how do we avoid overpressurization with the added pressure from the city? I'm probably overthinking this somewhere! That tends to be my M.O.! Micah Davis Ferguson Fire Design micah.da...@ferguson.com<mailto:micah.da...@ferguson.com> On Mon, Sep 25, 2023 at 12:02 PM Steve Leyton <st...@protectiondesign.com<mailto:st...@protectiondesign.com>> wrote: Micah: The best way to stabilize the pump discharge pressure and give yourself a (nearly) straight line suction pressure curve is to arrange the required secondary water supply as a break tank. Fill the tank with city water (recommend to manifold at least one automatic plus one manual fill; in my neck of the woods we use two automatic and one manual) and base your calculations on the lowest potential water level in the tank. We simply use the pump’s performance curve as a water supply assuming 0 psi suction head. Depending on water column height, your actual discharge pressure variation will be ≤ 5 psi, unless the tank is uniquely configured and multi-story. The foregoing is my opinion only and does not represent NFPA or the NFPA 14 Technical Committee, nor intended to serve as an interpretation of the standard. Protection Design and Consulting Steve Leyton, President T | 619.255.8964 x 102 | www.protectiondesign.com<http://www.protectiondesign.com/> 2851 Camino Del Rio South | Suite 210 | San Diego, CA 92108 Fire Protection System Design | Consulting | Planning | Training From: Micah Davis <micah...@gmail.com<mailto:micah...@gmail.com>> Sent: Monday, September 25, 2023 8:55 AM To: SprinklerForum <sprinklerforum@lists.firesprinkler.org<mailto:sprinklerforum@lists.firesprinkler.org>> Subject: [Sprinklerforum] Standpipe PRV Question Good morning, Forum! I've got a head-scratcher and am interested in the Forum's collective opinion! Important project parameters are as follows. - 42-story high rise with an automatic standpipe - Seismic Design Category - C - IBC 2018 - Fire pump supplied by city water supply - Secondary supply, as required by IBC 403.3.3, is a tank of adequate size - 305 psi @ 1000 gpm pump sized based on the feed from tank - Direct-acting pressure reducing valves on each floor Here is my issue. If I base my PRV settings on city supply, I cannot get 100 psi at the remote valves when calculating tank as supply. If I base my PRV settings on tank supply, I am over 175 psi discharge on the valve when calculating city as supply. If I try to get my settings using the city as static and the tank as residual pressures, there is no PRV setting that works. I have my opinions about what I think should happen here, but I want to see what the Forum thinks. I will not bother the group with what the design team is suggesting I do. Micah Davis Ferguson Fire Design micah.da...@ferguson.com<mailto:micah.da...@ferguson.com> _________________________________________________________ SprinklerForum mailing list: https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org To unsubscribe send an email to sprinklerforum-le...@lists.firesprinkler.org<mailto:sprinklerforum-le...@lists.firesprinkler.org>
_________________________________________________________ SprinklerForum mailing list: https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org To unsubscribe send an email to sprinklerforum-le...@lists.firesprinkler.org
