As an FPE using a particular hydraulic calculation software – if there is a pump on site, that is why you’re seeing the negative pressure. The software will publish that on the information sheet – however the real pressure required is shown on the graphical display. This would mean you’re 32 psi away from needing the pump – i.e., city supply will feed this particular design area without needing pump help – if a pump being present is the case….
Spencer Tomlinson, PE Owner, Fire Protection Engineer [red logo] Cell: 620-955-7293 From: Brett Peters <[email protected]> Sent: Thursday, November 20, 2025 10:25 AM To: Discussion list on issues relating to automatic fire sprinklers <[email protected]> Subject: [Sprinklerforum] Re: Hydraulic data plate. Honestly, I would say a FPE who's competency may be in question performed a calculation that doesn't work and an installer who's competency may also be in question just installed it and put the information on the hydraulic plate. I have come across similar issues before in performing tenant work in a building and have had to show the owner that the tenant system doesn't work because the base building never did work but the original installer and FPE got away with it somehow. (unfortunately there are some AHJ's who don't actually look or know what to look for when reviewing sprinkler drawings and calcs, they rely too heavily on the FPE being competent) 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<https://urldefense.proofpoint.com/v2/url?u=http-3A__www.proudline.ca_&d=DwMFaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=SMKi3MpB_L04QTNOI8wsXTbQAi8Ov0kr5kJ9QWv4K58&m=iY480h8Fmn62XdReaf00qpx_5UYadu9hD-qJwlhE9EsxLTlG6tjpEw_a1ahB73Mr&s=QIlST71tlcDfa93eFdL8aTFTwmEuHDra4sgYDzVYfpg&e=> On Thu, Nov 20, 2025 at 9:15 AM Joseph Zachary McTamney <[email protected]<mailto:[email protected]>> wrote: Hey everyone. I was looking over a hydraulic calculation plate, and the information is 435sqft, when supplied with water at the rate of 86.3GPM, at -32.0psi at the base of the riser. My question is "How can the supply pressure be -32.0psi?" Please explain and help me understand. Thank you. Get Outlook for iOS<https://urldefense.proofpoint.com/v2/url?u=https-3A__aka.ms_o0ukef&d=DwMFaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=SMKi3MpB_L04QTNOI8wsXTbQAi8Ov0kr5kJ9QWv4K58&m=iY480h8Fmn62XdReaf00qpx_5UYadu9hD-qJwlhE9EsxLTlG6tjpEw_a1ahB73Mr&s=eSifXsTknQYJA7Sg_v4obg5fNb61FVPdGgndsB70jx4&e=> _________________________________________________________ SprinklerForum mailing list: https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org<https://urldefense.proofpoint.com/v2/url?u=https-3A__lists.firesprinkler.org_list_sprinklerforum.lists.firesprinkler.org&d=DwMFaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=SMKi3MpB_L04QTNOI8wsXTbQAi8Ov0kr5kJ9QWv4K58&m=iY480h8Fmn62XdReaf00qpx_5UYadu9hD-qJwlhE9EsxLTlG6tjpEw_a1ahB73Mr&s=F7PVLn481m31RZArzGeuP4lH4L3IHoY_Nt1youqViN0&e=> To unsubscribe send an email to [email protected]<mailto:[email protected]>
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