What editions of #20 and #25 are referenced and following?
> On 03/06/2026 11:24 AM EST Fpdcdesign <[email protected]> wrote: > > > > Brett, here is Todd’s take (having seen a lot of pumps with issues lately): > > 1. Make sure you have the 10X pipe diameter distance between the backflow > preventer and the pump suction. > > 2. Based on the pump test, you have a 750 gpm pump rated at 70 psi and > producing only 65 psi at 750 gpm during the test. 63 psi would be a failed > test. How does that compare with previous tests? It could be an issue with > the pump or the suction piping. It is a 51 year old pump. Needs > investigating. > > 3. You need to get a hydrant flow test. I wouldn’t touch a pump project > without one. > > 4. You need to do a standpipe calculation to see what your demand is at the > pump discharge. > > 5. Don’t draw the public supply below 20 psi during a test. > > 6. There is a section in NFPA 25 that states that if a pump cannot be tested > to 150%, but it can be tested to the greater of system demand or rated flow, > then it can be considered acceptable. > > 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) > > > > > On Mar 6, 2026 at 10:52 AM, <Chris Dorn > > mailto:[email protected]> wrote: > > > > > > Questions > > > > 1. If testing confirms the standpipe cannot achieve 65 psi at 750 GPM, what > > is the recommended course of action? > > Install a higher pressure fire pump. 150% is not a requirement. 65psi > > definitely is though. Fire pumps make pressure, not water. > > > > 2. How should we address the requirement for a backflow preventer when pump > > suction is already low at 150% flow? > > > > Again not a requirement. > > > > 1. Are there alternative design approaches to meet the water authority’s > > requirement while maintaining proper pump operation? > > > > The water purveyor is protecting their system from a backflow situation. > > They are not going to let this go. > > > > 1. Water authority wants the backflow detector assembly on the suction side > > of the pump. > > > > Find the lowest pressure loss backflow device and go with it. > > > > Just my opinion. > > > > Chris > > > > > > > > > > > > > > > > From: Brett Barrall <[email protected]> > > Sent: Friday, March 6, 2026 9:55 AM > > To: [email protected] > > Subject: [Sprinklerforum] Backflow Preventer on Fire Pump Suction > > > > > > > > Hello! > > > > > > > > This is my first time posting, I’ll try to keep it short. > > > > > > > > We have a project with a new customer where the water authority is > > requiring a backflow preventer on the suction side of an existing fire > > pump. We want to confirm the proper approach due to potential hydraulic > > concerns. > > > > * Building height: 130 ft > > > > * System type: Wet pipe sprinkler and standpipe > > o Stair Tower 1: Class III combined automatic standpipe > > > > o Stair Tower 2: Automatic Class III standpipe > > > > o Standpipe flow requirements – 65 psi at 750 gpm (System installed 1975) > > > > > > > > * Fire pump: 70 psi at 750 GPM, city main supply > > > > * Hydrant flow test not performed, assuming static pressure at street > > around 75 psi. > > > > * No standpipe flow information. I recommended a standpipe flow test to be > > performed for documentation purposes. > > > > > > > > Existing Suction Piping > > > > * 4” × 6” concentric reducer at pump suction flange, recommended > > replacement with 4” × 6” eccentric reducer > > > > * 1975 water meter to be removed during backflow installation. Couldn’t > > find data sheets on this water meter to determine friction loss at system > > demand. > > > > > > > > Pump Test Data > > > > > > > > Flow > > > > Suction Pressure > > > > Discharge Pressure > > > > Churn > > > > 75 psi > > > > 155 psi > > > > 100% (750 GPM) > > > > 45 psi > > > > 110 psi > > > > 150% (1125 GPM) > > > > 5 psi > > > > 50 psi > > > > > > > > Sprinkler system demand: 268 GPM at 68 psi > > > > * Light Hazard > > > > * Apartments > > > > > > > > Concern > > > > * At 150% flow, suction is already 5 psi without a backflow preventer. > > > > * Adding a backflow preventer with additional fittings will introduce > > friction loss and will pull city main below zero during high demand. > > > > * Preliminary calculations indicate the standpipe may not achieve 65 psi > > residual at 750 GPM; (System installed 1975), verification pending a > > standpipe flow test. > > > > > > > > Questions > > > > 1. If testing confirms the standpipe cannot achieve 65 psi at 750 GPM, what > > is the recommended course of action? > > > > 2. How should we address the requirement for a backflow preventer when pump > > suction is already low at 150% flow? > > > > 3. Are there alternative design approaches to meet the water authority’s > > requirement while maintaining proper pump operation? > > > > 4. Water authority wants the backflow detector assembly on the suction side > > of the pump. > > > > > > > > > > > > Thank you for any guidance. > > > > > > > > > > > > > > > > > > > > Thank You, > > > > > > > > Brett Barrall > > > > Fire Sprinkler Designer > > > > [email protected] mailto:[email protected] > > > > > > > > [image004.jpg@01D445D6] > > > > > > > > 50 S. Museum Road, Reading, PA 19607 https://goo.gl/maps/A3D5Y6oTJUT2 > > > > Office: 610-775-1200 ● Toll Free: 1-800-344-4012 > > > > www.bsgi.com https://www.berkshiresgi.com/ > > > > Satellite Offices in York & State College > > > > ● PA State Contract & Costars Participating Vendor ● > > > > ----- Email Disclaimer ----- > > This email and any files transmitted with it are confidential and are > > intended for the named recipient(s). If you are not the intended recipient, > > you are hereby notified that you have received this communication in error > > and that any copying, disclosure, dissemination, distribution or review of > > it or its contents is prohibited. If you have received this email in error, > > please notify the sender and immediately delete this email from your system. > > > > > > > > _________________________________________________________ SprinklerForum > > mailing list: > > https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org > > To unsubscribe send an email to [email protected] > > > > _________________________________________________________ > SprinklerForum mailing list: > https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org > To unsubscribe send an email to [email protected] >
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