Hey Ken, As has already been stated by others, I believe the intent is to remove as much air from 'each wet system' as possible. 'System', in this case, is any piping network isolated from the rest of the upstream system by isolation valving be it a check valve or a shutoff valve.
Support for this may be found on page three of the 'Origin and Development' at the beginning of NFPA 13 (2022). While multiple floor control valve configurations may be on a single wet-pipe system, it is unlikely that air trapped in piping in lower floors will migrate through these valve configurations =, and the common low points in the piping configuration, to the single high-point connection in the top floor piping. Also, when work is done on a single level (not at the highest level), piping is likely drained on that floor only. Air will be reintroduced into this piping at high points upon refilling which, without having a single high-point vent on that floor (downstream of the floor control valve) would have to migrate back through multiple open floor control system valving configurations and up to the top floor...which I think is unlikely. Annex A16.7 provides further rationale for removal of as much air from wet-piping networks as possible from a single location on metal systems to reduce corrosion and is currently up to the discretion of the designer. I would contend that this is on any system segment that can be isolated while leaving the remainder of the system in service. Furthermore, the annex section also recommends each wet pipe sprinkler system to be vented every time the system is filled. On a multi-floor controlled wet pipe system without venting on each floor, I would contend that is will result in multiple problems for contractors trying to do their due diligence and purge these systems. Even though not outright required, I believe at least one air vent should be downstream of each isolatable wet-pipe system section. It is definitely a 'good practice' as you have suggested. Hope this helps, Ryan L. Hinson, PE*, SET** \ Burns & McDonnell Associate 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 From: Ken Wagoner <[email protected]> Sent: Monday, October 9, 2023 10:43 AM To: [email protected] Subject: [Sprinklerforum] Air venting Forumites, I'm working on a multi-story building protected per NFPA 13. As each floor has a separate control valve, is a means to vent trapped air required on each floor? Or is it only required at the highest level of the building? My thinking is that each floor has a separate fire sprinklers system. Any thoughts? Ken Wagoner, SET Parsley Consulting 500 West Mechanic Street Harrisonville, Missouri 64701-2235 Phone: (760) 745-6181 Visit the website<https://linkprotect.cudasvc.com/url?a=http%3a%2f%2fwww.parsleyconsulting.com%2f&c=E,1,Y5zKJKPEh1mBEBqSR-VE9cUKl5y-eyP8BpvmE_5j9ZqW2eJbNphYzrCMBZ-2YuX6d-RRkHI4gQ1FV-cvOeCfRC58uZS9NiToZv2mx7909oCqLvCW_n5hDHeK&typo=1>
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