I think you’re blurring 403.3.2 and 403.3.3. If you need two separate city connections based on building height, you can still fill a break tank with supply lines connected to separate main legs as prescribed. 403.3.3 doesn’t say anything about the connection configuration of pump to tank or primary/secondary or anything that prescriptively triggers two separate connections. UNLESS you take suction directly from a city main and then have to make a separate connection to a tank. Using a break tank checks all the boxes IMHO, as you stabilize the suction pressure, you have redundancy, you have (barring catastrophe) a reliable water supply AND it’s all a lot simpler to design, build and maintain. That last part is the most important and what we’re ultimately seeking with a standpipe water supply is adequacy and reliability. Of course all of this assumes rigorous ITM to make sure it’s full, but I reiterate that the point of the secondary water supply is to hedge against interruption of the primary and assure an adequate water supply. Not two adequate water supplies, just one. The break tank resolves and the disparate discharge pressure issue that Micah originally asked about.
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: Brett Peters <[email protected]> Sent: Monday, September 25, 2023 12:11 PM To: Discussion list on issues relating to automatic fire sprinklers <[email protected]> Subject: [Sprinklerforum] Re: Standpipe PRV Question Steve, I understand the argument but I think that eliminates having two supplies to the fire pump, if you are only filling the tank and using the tank as the sole supply to the fire pump then you only have on supply, what happens if in the case of some type of event you actually lose the tank but have city water supply, you need the the city supply supplying the fire pump as well as the tank or you essentially are still looking at only one supply to the fire pump and assuming that the tank will never fail as opposed to having city supply and tank supply to the pump which would be 2 independent sources. Thanks Brett Peters General Manager Installation & Design Proudline Fire Protection Services Ltd. [email protected]<mailto:[email protected]> 780 490 7602 office ext 202 780 490 7605 fax 780 777 0568 cell 780 718 2676 24h Visit us at www.proudline.ca<http://www.proudline.ca/> Proudline now offers ULc listed monitoring services, please contact [email protected]<mailto:[email protected]> for more information [https://ci3.googleusercontent.com/mail-sig/AIorK4wRo6r0eNDUWx8YR-4XJLvwcnouQn_xEZH_HIb4jDbepWtON2RWC-ekzvZHKtncFOQqPcNQfzM] [https://ci3.googleusercontent.com/mail-sig/AIorK4yJVI287VPLDWiW9maE2Np3U4CdszCY9deeyaLl8DM90wlBd7pnuOZV9U-swv-7gWN_24py6vo] [https://ci3.googleusercontent.com/mail-sig/AIorK4wlGmqj6Ja06DKOIMLPvEE8B2W8fT_TPPA3w-4JfqygLq9n77ECSni09YLIVICXJYzWo4Z0PjU] [https://ci3.googleusercontent.com/mail-sig/AIorK4zEgPbs279KVEfWIpIiWNLel8zAlcloW9dNXGLTaE1cMz88CRkmg17fju5BQB_iIzhWK20DUL8] [https://ci3.googleusercontent.com/mail-sig/AIorK4z7J0kfmSGA8jKvDK0pTqW3KQlc5v-tYcWosmy5W7pdok462Gzu_9Ft7UK9oJUWDT1DzhQ4hUU] [https://ci3.googleusercontent.com/mail-sig/AIorK4wTVHoTZxkppBoWSCTFnGLgGTq0apivi8sNvWPyBsloO0mmy8ZYu4Ax854jo7ihTMFyeYeOceg] [https://ci3.googleusercontent.com/mail-sig/AIorK4xwBWEOX5v9mpza4Jqf9lOKSwThBNvyIO7Rl-Cxo7NRiV7p70C0f1biwbh44Y-iIA5GcmD1MCo] [https://ci3.googleusercontent.com/mail-sig/AIorK4yPfO1HdtbQPYiKlYE38cwc88ABhX7xN1nh0fCK5LjFXjKplJggk3Xn6_XypmtMWyADKR7ZRGk] On Mon, Sep 25, 2023 at 1:05 PM Steve Leyton <[email protected]<mailto:[email protected]>> wrote: 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 <[email protected]<mailto:[email protected]>> Sent: Monday, September 25, 2023 9:47 AM To: Discussion list on issues relating to automatic fire sprinklers <[email protected]<mailto:[email protected]>> 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 <[email protected]<mailto:[email protected]>> Sent: Monday, September 25, 2023 9:17:40 AM To: Discussion list on issues relating to automatic fire sprinklers <[email protected]<mailto:[email protected]>> 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 [email protected]<mailto:[email protected]> On Mon, Sep 25, 2023 at 12:02 PM Steve Leyton <[email protected]<mailto:[email protected]>> 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 <[email protected]<mailto:[email protected]>> Sent: Monday, September 25, 2023 8:55 AM To: SprinklerForum <[email protected]<mailto:[email protected]>> 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 [email protected]<mailto:[email protected]> _________________________________________________________ SprinklerForum mailing list: https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org To unsubscribe send an email to [email protected]<mailto:[email protected]> _________________________________________________________ SprinklerForum mailing list: https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org To unsubscribe send an email to [email protected]<mailto:[email protected]>
_________________________________________________________ SprinklerForum mailing list: https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org To unsubscribe send an email to [email protected]
