Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit

Auto Vent No 67 Auto Bleeder

Gregory_2 Member Posts: 30
edited January 2020 in Domestic Hot Water
Do I need to completely drain the system to replace? I have 3 story 1 zone house
and less that 5 lbs of pressure in the system. If I turn off unit can I replace without
draining the whole system?
the auto bleeder is at the top


  • Jamie Hall
    Jamie Hall Member Posts: 17,121
    You may have to drain it down slightly to avoid getting wet.

    However, if you have a 3 story house with hot water heat, 5 pounds of pressure (I presume in the basement at the boiler?) is nowhere near enough. You should have at least 15 pounds pressure in the system when it's cold; check that before you work on that bleeder, because if it's really only 5 pounds when you crack that vent it's going to such air into the system and you'll have to purge the whole thing. At least you wouldn't get wet...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Gregory_2
    Gregory_2 Member Posts: 30
    Jamie thank u. And yes that’s the issue I keep losing pressure and I think it’s the auto bleeder
    I had another thread going on this forum about it. Thanks
  • Gregory_2
    Gregory_2 Member Posts: 30
    another quick question. should the old one come off by hand?
    and will I need dope or tape for the threads on the new one

    thanks for your help
  • SuperTech
    SuperTech Member Posts: 1,691
    It might come off by hand, or you may need a wrench. You can use either pipe dope or Teflon tape, or both of them together.
  • HomerJSmith
    HomerJSmith Member Posts: 1,372
    Why do you have such a large air vent on the third floor?

    Caleffi makes a hygroscopic air vent that is very good and in combination with their 1/8" NPT Male Service Check Valve allows changing the vent easy.