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Barnes&Jones Big Mouth plug

josephc Member Posts: 39
i just received a BJ-3BM Barnes and Jones Big Mouth 3/4" Main Air Vent and looking inside i see the plug or disc floats or pivots on the shaft coming from the diaphragm. is that its proper design or is it supposed to be fixed to the shaft and perfectly perpendicular to the seat? It is also gapped pretty far from the seat in the cold position - is that normal.

can its action be tested using external heat like a heat gun/blow dryer or placement on top of a radiator?


  • kenlmad
    kenlmad Member Posts: 56
    Pivoting disc is normal.

    I've tested other vents using boiling water on my stove. Maybe you can attach a hose and try blowing through the vent after the boiling water actuates the sealing disc. Or hold the hot boiled vent upside down over the sink with tongs to see if it holds water. There may be better ways to test the big mouth.