Is there a calculation method for sizing of air vents at the top of a sprinkler system riser?
NFPA 13 says 1/2-inch (15 mm), for a manual valve, but is there a way to calculate what this should be for a large system?
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1/19/2022 07:37:36 am
NPFA 13 states a minimum size. I do not see why you need/would want to go any larger than 1/2", especially if you use an automatic air vent (Potter offers UL listed & FM vents).
1/19/2022 07:56:58 am
I'm not sure why you'd need a vent larger than 1''? the only thing that would change as you increase the size of the vent is the time it takes the air to vent out. the velocity would remain the same as there is near constant pressure behind the air pushing it out. Also I'd lean to the smaller side as its easier to control how much water would inevitably burp out. Say you have a faulty/dirty ball float in the vent chamber you can shut it off and have less water splash about.
1/19/2022 08:42:24 am
NFPA 13 only discusses a minimum size.
1/19/2022 09:36:21 am
Min. Vent per NFPA 13, but some manufacturers provide guidance.
1/19/2022 09:38:20 am
I agree with the other posts that 1/2" is fine for manual venting like AGF 7910. The preferred method we see most often with our PURGEnVENT product line is the automatic air vent like our Model 7900A which vents through .09 orifice
1/19/2022 10:30:52 am
I agree 1/2" Min. per NFPA 13.
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