What size/model backflow and flow rate? Many N shaped RPZs are up around 15 psi loss when you’re running them at the kind of flows a 150% test would see for a given suction size pump. Also the larger units never drop below about a 10 psi loss no matter what. If you’re losing that much at or near churn I’d suspect a problem with the backflow itself.
Mike Morey 2025 NFSA Top Tech Champion • NICET IV • CFPS Project Estimator • Fire Protection Group Shambaugh & Son, LP an EMCOR Company 7614 Opportunity Drive • Fort Wayne, IN • 46825 direct 260.487.7824 / cell 260.417.0625 email mmo...@shambaugh.com<mailto:mmo...@shambaugh.com> 24/7<outlook-data-detector://2/> SERVICE LINE 888.217.7055<tel:888.217.7055> [cid:image001.jpg@01DBE503.CB22CE00] From: Fpdcdesign <fpdcdes...@gmail.com> Sent: Tuesday, June 24, 2025 12:17 PM To: Discussion list on issues relating to automatic fire sprinklers <sprinklerforum@lists.firesprinkler.org> Subject: [Sprinklerforum] Re: [EXTERNAL] Backflow turbulence The water supply tested in the street to 38 psi with less than 5 ft elevation to the pump room. The suction pressure they are getting during the pump test is 15 Todd Williams Fire Protection Design/Consulting Stonington, CT 860-608-4559 On Jun ZjQcmQRYFpfptBannerStart This Message Is From an External Sender This message originated outside your organization. ZjQcmQRYFpfptBannerEnd The water supply tested in the street to 38 psi with less than 5 ft elevation to the pump room. The suction pressure they are getting during the pump test is 15 Todd Williams Fire Protection Design/Consulting Stonington, CT 860-608-4559 On Jun 24, 2025 at 11:39 AM, <Craig Prahl<mailto:craig.pr...@jacobs.com>> wrote: Are suction pressures low due to the water supply? Since there is a BFP, I assume you’re drawing from a city service, correct? Got any data on that system? Craig Prahl | Jacobs | Fire Protection SME – EV, AM, DC, Special Hazards craig.pr...@jacobs.com<mailto:craig.pr...@jacobs.com> | www.jacobs.com<https://urldefense.com/v3/__http:/www.jacobs.com/__;!!KZTdOCjhgt4hgw!-_khxU8gU0_6jc895I7kRbnU8JghRDsWgqOblZ4jr7Qp2IVbR30VYw_hWvNFtphnl0uWpB9KIvbYi1pvZz4$> 1041 East Butler Road Greenville, South Carolina 29606 CONTACT BY: Phone 1-864-676-5252, Email or MS TEAMS From: Fpdcdesign <fpdcdes...@gmail.com<mailto:fpdcdes...@gmail.com>> Sent: Tuesday, June 24, 2025 10:45 AM To: Sprinklerforum <sprinklerforum@lists.firesprinkler.org<mailto:sprinklerforum@lists.firesprinkler.org>> Subject: [EXTERNAL] [Sprinklerforum] Backflow turbulence I am working on an untestable fire pump with an “N” shaped RPZ in the suction line. They (just) have the 10X diameter distance on the feed, but the suction pressures are very low (15 psi). It seems that an “N” shaped device would create a lost I am working on an untestable fire pump with an “N” shaped RPZ in the suction line. They (just) have the 10X diameter distance on the feed, but the suction pressures are very low (15 psi). It seems that an “N” shaped device would create a lost more turbulence than a standard straight one. Consequently, should the distance of straight pipe requirement be greater for this arrangement? Todd G Williams, PE Fire Protection Design/Consulting Stonington, CT 860-535-2080<tel:860-535-2080> (ofc) 860-554-7054<tel:860-554-7054> (fax) 860-608-4559<tel:860-608-4559> (cell) ________________________________ NOTICE - This communication may contain confidential and privileged information that is for the sole use of the intended recipient. Any viewing, copying or distribution of, or reliance on this message by unintended recipients is strictly prohibited. If you have received this message in error, please notify us immediately by replying to the message and deleting it from your computer. _________________________________________________________ SprinklerForum mailing list: https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org<https://urldefense.com/v3/__https:/lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org__;!!FaxH778!YPJnKEAAeBMNczQSgCWFRVOmkW4hd70Wt4L4gQOqqbgjvlufzro1mlFMbuTfzlf0lzI9yTjd5rIepp0F9z8$> To unsubscribe send an email to sprinklerforum-le...@lists.firesprinkler.org<mailto:sprinklerforum-le...@lists.firesprinkler.org> This message is for the named person's use only. It may contain confidential, proprietary or legally privileged information. No confidentiality or privilege is waived or lost by any mistransmission. If you receive this message in error, please immediately delete it and all copies of it from your system, destroy any hard copies of it and notify the sender. You must not, directly or indirectly, use, disclose, distribute, print, or copy any part of this message if you are not the intended recipient.
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