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Hoffman #75 Main Vent

bobbob Member Posts: 70
Does not seem to function consistently. Tried the vinegar soak. IS THERE A WAY TO DISASSEMBLE TO CLEAN? Will it do any good, or has it become faulty with age?


  • Jamie Hall
    Jamie Hall Member Posts: 23,536
    There is no way that I know of to take those apart. At least not so they can be put back together. If it won't open after a vinegar soak and a sharp rap or two, it's done.

    And check your boiler pressure. That vent has a maximum working pressure of 3 psi, and a maximum pressure before damage of 15 psi.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Steamhead
    Steamhead Member Posts: 16,940
    @bobbob , time to replace it. How long is the steam main it serves, and what pipe size?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • bobbob
    bobbob Member Posts: 70
    That vent was in use since we bought house 21 years ago. My 0-5 lb pressure guage reads under 4 ounces
    max. Thanks for the responses. These are pretty cashy. Hoped it could be fixed...
    JUGHNE Member Posts: 11,089
    I think the green paint dates it way back.

    A Gorton 2 will vent twice as much for the same money....they have gotten some bad reviews lately...hopefully the quality control has improved.

    A B&J big mouth will vent 3 times as much as your 75...a little more money and also no float to stop water if that happens.
  • ethicalpaul
    ethicalpaul Member Posts: 5,757
    Yeah I wouldn’t buy a 75 today. For a real bargain, try this one, functionally equivalent to a Gorton #1

    If your pressure stays the same or goes a little lower in the startup phase, then you’re all set
    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el
  • bobbob
    bobbob Member Posts: 70
    The problem with this vent was it is not closing--at least, not fully. I tapped on it several times and it closed, but I can't be there to tap every time the boiler cycles. It may have been here long before I became the HO in 2000. I intend to go ahead and replace it as you have advised. Thanks again for you all's inputs!