Big Mouth vent installation question

jerseyguy82

I just received two of the Barnes & Jones big mouth air vents to replace two very old Gorton #1's in my main lines. I understand using a 5/8" allen key to seat the 3/4" nipple, but what about the brass union? Is ptfe dope on the union threads sufficient, or is something needed on the mating faces? Also how tight should the union be torqued down? Sorry I don't have much experience. Learning about steam so I can sort out many problems in our heating system.

EBEBRATT-Ed

You don't "have" to put anything on the union fitting. It is made to not leak without any dope or sealer.

But, if it was me I would put some "never seize" or "anti seize" a little on the face and a little on the threads. It will make removal easier. Auto supply stores or big box stores should have it.

Some will use a little pipe dope

Fred

Don't use anything on the making surfaces and you don't need to use anything on the union threads. The mating surfaces of the union will prevent any leakage. Just use some tape on the threads that go into your pipe. Tighten it snug. You don't have to apply a lot of torque. If you see it leaks anywhere, just tighten it a little more.

BobC

When I mounted mine I used Oaty pipe dope on the threads and left the mating surfaces bare. After getting the whole vent mounted finger tight I used a wrench to tighten the union nut and that also tightened the threaded connection.

I'm amending because the above might be miscontrued - no pipe dope on the union nut threads, just on the mounting threads.

Bob

Sailah

Don't use anything on the union nut threads or mating surface, just the NPT threads.

-signed, the guy who invented the Big Mouth