Will Brass Clappers Hold 12 psi of Supervisory Air?

6/26/2025

We're installing a manual dry standpipe system that will have 12 psi of supervisory air. This is my first supervised dry standpipe in [redacted by original author to protect author's extreme age] years in the industry.

The FDC has 3 brass clappered snoots supplying a 6" main.

I'm assuming we'll need to install a 6" rubber-faced check valve near the FDC to hold the air. However, you know what they say about 'assuming'.

Therefore, I'll ask the FP Pro world: Is there any chance those brass clappers will hold 12psi of air?

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3 Comments

Anthony

6/26/2025 08:12:25 am

The FDC isn't the air seal its the check valve after the FDC that'll hold back the air pressure. That's a one way valve and will have a seal.

Dan Wilder

6/26/2025 08:40:22 am

You'll either need individual clapper snoots to a manifold (flush style) or a larger single check valve (spring loaded preferably) to hold back the air. The standard clappers will just swing and are not watertight, even lesser so for air.

Leave room for a drum drip as the velocity checks won't work on the pressure side of that check valve and it will likely be on a lower section of the pipe and drainage will be needed.

Jack G

6/26/2025 12:24:17 pm

The intent is an fdc inspection 3 times a year ( NFPA-25 )
Also the intent is for the 12 psi (is from) the clappers of the fdc to the tops of the dry standpipe
As mentioned above snoots with threaded caps/ plugs , would be a great idea. A check valve after the fdc, would shield the small space between the fdc and the check from the supervisory air.
Rather then drill a hole in the clapper for equalization, I think a better method would be to install a drain line between the fdc side and standpipe side. The drain valve ( closed ) can be beneath the air- equalization line, so you get a drain for the sp and . 12 psi air supervisory.
I would mention the hose valves should have proper gaskets,
And some sort of air relief on top of the standpipes as when energized the fireman would be pushing 12 psi of air out.
In the past I ve even put emergency trip systems, like you’d have on a deluge system, above each hose valves so the fireman can control the release from each valve. (/ was requested by an A&E)

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Will Brass Clappers Hold 12 psi of Supervisory Air?

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