Steve, Velocity is FPS, Flow rate is GPM.
Velocity is related to the pipe diameter and flow rate. Flow rate affects velocity as related to pipe diameter. So it’s just math. NFPA 13 does make a statement in regards to flow rate that requires it to be either the hydraulically calculated flow rate plus hose allowance, or the flow necessary to create a 10 fps velocity, or the maximum flow rate available to the system. Your choice. Craig Prahl | Jacobs | Fire Protection SME – EV, AM, DC, Special Hazards [email protected]<mailto:[email protected]> | www.jacobs.com<https://urldefense.com/v3/__http:/www.jacobs.com/__;!!KZTdOCjhgt4hgw!-_khxU8gU0_6jc895I7kRbnU8JghRDsWgqOblZ4jr7Qp2IVbR30VYw_hWvNFtphnl0uWpB9KIvbYi1pvZz4$> 1041 East Butler Road Greenville, South Carolina 29606 CONTACT BY: Phone 1-864-676-5252, Email or MS TEAMS From: Steve Leyton <[email protected]> Sent: Tuesday, January 28, 2025 5:10 PM To: Discussion list on issues relating to automatic fire sprinklers <[email protected]> Cc: Brent Kearney <[email protected]> Subject: [EXTERNAL] [Sprinklerforum] UG flush - minimum flow rate Sprinkies: Section 6. 10. 2. 1 (2022 edition) of NFPA 13 prescribes a minimum flow rate of 10 fps for flushing, and Table 6. 10. 2. 1. 3 offers flow minimum rates for different pipe diameters that will achieve that velocity. My question is (the one Sprinkies: Section 6.10.2.1 (2022 edition) of NFPA 13 prescribes a minimum flow rate of 10 fps for flushing, and Table 6.10.2.1.3 offers flow minimum rates for different pipe diameters that will achieve that velocity. My question is (the one that’s been posed to me by an inspector) is whether or not there’s an absolute minimum flow rate in GPM based on size. A contractor has proposed to flush a 4” UG through a 1½” connection with “several hundred feet” of 1½” hose to a collection point. The inspector is questioning (and I’m wondering also) if it is required or is the intent to flush to at least the demand of the system, or some other benchmark flow? For whatever it’s worth Table 6.10.2.1.3 (10.10.2.1.3 in NFPA 24) starts at 2”, so I’m also curious if that implies that 2” is the minimum allowable size for a flushing connection? [cid:[email protected]] Steve Leyton, President T | 619.255.8964 x 102 | www.protectiondesign.com<https://urldefense.com/v3/__http:/www.protectiondesign.com/__;!!B5cixuoO7ltTeg!FYB8XasgVWnhNdjtbeb4TYfsWfjz_16xbIWLAcLriSEZmzvEAyq6uBBQbSp7NIU9xL3q0QpvrBpmjZA09ZN9fvo$> 2851 Camino Del Rio South | Suite 210 | San Diego, CA 92108 Fire Protection System Design | Consulting | Planning | Training ________________________________ 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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