FWIW, Joe Meyer provides a nice explanation of the potential for error from flowing smaller amounts of water versus higher flows (which this discussion is about) in the following YouTube vid: https://www.youtube.com/watch?v=8YpogorxFSc
We recently performed refinery-sized firewater flow testing to the 25% drop previously required in order to extrapolate theoretical values or system demand (of approximately 6600 gpm) per NFPA 291 from a southwestern US city with city assistance. Our flow test results of 116/87/6949 (which achieved both) were used to eliminate over $1,000,000 in scope for an onsite FW storage tank upstream of new fire pumps. Like Craig, I also have my doubts as to whether modeled results would have been in the neighborhood and would not use theoretical flow unless verified with actual water on the ground for the reasons explained in the blog. It should be noted that a 10% pressure reduction required by some fire codes is smaller than the possible 40% error that could be present in a water flow test due to the ‘sample size’ of the water supply taken in a flow test as presented, where only small amounts of water are actually flowed. Hope this helps, Ryan L. Hinson, PE*, SET** \ Burns & McDonnell Senior Fire Protection Engineer O 612-900-3755 \ M 763-688-4045 \ F 952-229-2923 [email protected]<mailto:[email protected]> \ burnsmcd.com<http://www.burnsmcd.com/> 8201 Norman Center Drive, Suite 500 \ Minneapolis-St. Paul, MN 55437 *Registered in: AK, LA, MD, MN, PA, TX, & UT **NICET IV - Water-Based Systems Layout [cid:[email protected]] From: Prahl, Craig <[email protected]> Sent: Wednesday, August 31, 2022 10:10 AM To: Discussion list on issues relating to automatic fire sprinklers <[email protected]> Subject: [Sprinklerforum] Re: [EXTERNAL] Hydrant flow tests Having experienced bogus results from computer modeling on more than one occasion, nothing matches the actual flow of the hydrant systems. Most recently I got a water report from a local municipality who generated the info via their water modeling software. It said I could expect 6700 gpm from the system……. via 8” lines at 10 fps! Nope, don’t think that’s going to be a real thing. Craig Prahl | Jacobs | Group Lead/SME – Fire Protection | [email protected]<mailto:[email protected]> | www.jacobs.com<https://nam12.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.jacobs.com%2F&data=05%7C01%7Crhinson%40burnsmcd.com%7Ce93b3c17fb5e4a7addbb08da8b63237e%7Cbfbb9a2b6d994e78b3c795005d555c8b%7C0%7C0%7C637975555193854225%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=eKLvK0U2XoKe32DI9LSrWzu0oHRqmEPIUBXPjZWFnNM%3D&reserved=0> 1041 East Butler Road Greenville, South Carolina 29606 CONTACT BY: Phone 1-864-676-5252, Email or MS TEAMS From: Rick Matsuda <[email protected]<mailto:[email protected]>> Sent: Wednesday, August 31, 2022 9:51 AM To: [email protected]<mailto:[email protected]> Subject: [EXTERNAL] [Sprinklerforum] Hydrant flow tests I know that an accurate flow test is critical for the sprinkler system design, but I’ve heard several discussions recently about water conservation during our drought conditions across the SW states. With all our technology, is it possible to develop an accurate computer modeling program for water departments to use in lieu of flow tests? Even with the program, I think there would still be a need for some flow tests to verify the program results, but maybe not as many as now. I’m not taking any pro/con position regarding this issue. I’m just providing food for thought for the future as our need for water increases and our resources diminish. Adequate water is the key for our industry. It’s ironic cause we get more wild fires due to the drought, and then we have to use more water to fight the fires. Rick Matsuda ________________________________ 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.
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