I have used the static without the backflow loss in the past but I noticed with the SprinkCad software I am running it uses the mfg curves and it was showing less static than I had figured. If I take into account the BFP loss I can eliminate 6 pressure reducing hose valves…..Looks like I will err on the side of caution and design them in.
Thanks, Dewayne *From:* Sprinklerforum [mailto: sprinklerforum-boun...@lists.firesprinkler.org] *On Behalf Of *Steve Leyton *Sent:* Wednesday, January 11, 2017 8:12 AM *To:* sprinklerforum@lists.firesprinkler.org *Subject:* RE: Static pressure after backflow preventer My understanding of backflow performance and the mapping of those curves is that the devices impose more pressure loss at opening than at closing. So that spike at 0 GPM is an accurate reflection of the higher pressure loss that occurs at the initiation of a flow event and it almost always ramps right back down once flow rate gets into the dozens or above 100. But at zero flow, we've always used the ambient static and my vague recollection is that several years ago I confirmed this either with our local Wilkins rep are their factory in San Luis Obispo. I do know that we have never been corrected by an AHJ or third party consultant so I'm 99.9% sure that this is the accepted best practice. Steve L. -------- Original message -------- From: Dewayne Martinez <dmarti...@total-mechanical.com> Date: 1/11/17 5:41 AM (GMT-08:00) To: sprinklerforum@lists.firesprinkler.org Subject: Static pressure after backflow preventer Is there really a pressure loss at 0gpm flow for backflow preventers like the curves show? I am trying to figure out my static pressure on a floor level with a fire pump at churn and it needs to be accurate. Thanks, Dewayne Martinez Fire Protection Design Manager *TOTAL Mechanical* *Building** Integrity* W234 N2830 Paul Rd. Pewaukee, WI 53072 dmarti...@total-mechanical.com Ph: 262-522-7110 Cell: 414-406-5208 *http://www.total-mechanical.com/ <http://www.total-mechanical.com/>* [image: cid:image001.jpg@01D09EDA.87B946F0] [image: cid:image002.jpg@01D09EDA.87B946F0] [image: cid:image003.jpg@01D09EDA.87B946F0] [image: Top Workplaces 2015] *TOTAL Mechanical voted “Top Workplace” for a 4th consecutive year. *
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