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Boiler Heating System: Bleed Air from Zone

Konrad Member Posts: 1
Can’t figure out how to bleed air out of my boiler system. 


  • Konrad
    Konrad Member Posts: 1
    I noticed under the expansion tank the drain should let me clean zone one but I can’t figure out what could be done  to remove the air from 1st floor
  • Jamie Hall
    Jamie Hall Member Posts: 23,536
    Are there any bleeders on the radiators? There should be -- and the first thing to do is to make sure you have enough pressure in the system (15 psi cold as a sort of general rule of thumb) and open each bleeder in turn. Close it when you get a good stream of water and go on to the next. Then if you still have air in the system, you'll need to purge it.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    edited March 2021
    Power off. For the basement zone (I think), close Red. Put a hose on Blue. Manually open that zones zone valve.
    Now all at the same time, lift lever on green, open blue, and purge zone thru hose into a sink, preferably a bucket in the sink so you can see the air bubbles.
    The whole time you'll want to keep the pressure up around 15 lbs.
    When the zone is free of air, close Blue & Green at the same time. Close the manually opened zone valve.
    The most important thing is to maintain pressure.
    For what appears to be the other zone:
    You have to find a shut off valve for that zone, similar to the other zone.
    If you can show it to me, just to be sure, you'll do the same thing:
    Manually open that zones zone valve. This time you'll open green, but you probably have to purge thru the boiler drain.

    Then open the 2 shut offs, power the boiler back up. The manually opened zone valve(s) should power close

    There was an error rendering this rich post.

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,153
    edited March 2021
    I have some questions for you to answer. The type of radiator will determine if you get the air out by purging as in the basement zone or you vent the radiators individually.

    Think Like Water in your mind's eye. If you have a "Loop" of 3/4" baseboard connected by 3/4" pipe then the inside of the entire loop looks like the same thing to the water passing thru it. It is a 3/4" inner diameter tube with some turns but no Tees. No Tees means there are no choices to make for the water to decide on which way to go. Only one path. This you can purge!

    On the upper 1" pipe there are some tees to each radiator or loop or connector. Because there are choices you can't "Purge". You see, once the water decides on the path of least resistance, the air in the rest of the zone will just stay there. The closest radiator, or lowest loop, or biggest diameter pipe, or the shortest run, or some other path will be the least resistance and the other branches of all the other tees will all be ignored.

    With a "connector" emitter, you may have a diverter tee (MonoFlo) system where each connector has a supply and return connected to the same 1" loop in the basement. these were popular in the late '40s, '50s, and '60s. If you have these "convector" radiators.

    Then you are looking for something like this inside the cover (that is most likely painted on),

    after you get the cover, off look for something like the screwdriver slot in the tiny valve sticking up.

    Show us your radiator Pornography pictures so we can all oogle at them.

    So the Questions:
    What radiator or emitters do you have upstairs?
    How are they connected to the 1" pipe?

    Respectfully submitted,

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?