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Automatic air bleed, but how?

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Stillkickin
Stillkickin Member Posts: 4
in Domestic Hot Water

How does my Maid-O-Mist automatic Auto Vent system work? It has a valve core like a car tire. How is any air going to be expelled past that? Wondered for years. Thanks

IMG_5306.JPG IMG_5310.JPG

Comments

  • mattmia2
    mattmia2 Member Posts: 13,436

    there is a float attached to that needle and seat. if the can gets enough air in it the float falls enough to open the needle.

  • mattmia2
    mattmia2 Member Posts: 13,436

    caleffi and a few others have literature with cutaways

  • hot_rod
    hot_rod Member Posts: 25,323

    commonly called a float vent

    It is into to ho on a high point in the system, or screw into an air purger

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,895
    edited July 14

    Hi, Vents like this one are designed so they can be disassembled and cleaned if needed. 😉

    https://www.supplyhouse.com/Amtrol-701-30-1-4-MPS-Float-Air-Vent?utm_adgroupid=1239150722961757&utm_targetid=pla-4581046494508461&utm_product_id=701-30&utm_matchtype=e&utm_adtype=&utm_adgroup=Hydronic%20System%20Components_X_X_X&utm_searchquery=repairable%20float%20vent&utm_category=Heating

    Screenshot 2025-07-14 at 12.49.05 PM.png

    Yours, Larry

    Stillkickin
  • hot_rod
    hot_rod Member Posts: 25,323

    Most brands have a screw top to allow cleaning or replace the cap and valve.

    Screenshot 2025-07-14 at 2.13.13 PM.png
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 10,743

    The part of the vent that looks like a Schreader valve is not actually a Schreader valve.  They are not spring loaded to self close like you would find on a tire or a refrigeration system gauge port.  The valve actually closes by means of a float mechanism that replaces the spring’s function of the Schreader valve.   When the float is high the valve is closed.  When the float drops, the valve is opened and will allow air in the can to be released.  Once the air is released, the float will rise and close the valve.  

    The part in the center of the valve, that you might want to depress will manually force the valve open against the pressure of the float mechanism (just like you would let air out of a tire), but doing that will often cause the float mechanism to fail since the water ends up higher that the design of the valve normally allows.  Do not check the valve by pushing the center of the valve down until you get water out of the vent. Do that too many times and you will have a defective vent in short order.    

    Edward Young Retired

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

    Stillkickin
  • HydronicMike
    HydronicMike Member Posts: 76

    Put a mini ball valve on it to make cleaning and change outs easy. I’ve only used Caleffi ones for the last 5 years. Better built/made and able to clean repair. The one you have pictured, to me, is a throw away item.

    EdTheHeaterMan

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