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Maid-O-Mist (Jacobus) steam radiator vents

Tuggy Member Posts: 46
edited March 2023 in Radiant Heating

Haven't found a definitive answer on this.

I have different caps for different venting rates, 4,5,6,C,D.

Is leaving the vent uncapped the same as putting on a D size cap insofar as the amount CFM air vented? And will the vent work exactly the same? Or is there some caveat?

Mad Dog_2


  • Big Ed_4
    Big Ed_4 Member Posts: 2,806

    Your thinking too much , I would leave it up to who designed the valve .

    There was an error rendering this rich post.

  • Tuggy
    Tuggy Member Posts: 46

    I have more vents than D caps.

  • ethicalpaul
    ethicalpaul Member Posts: 5,735
    edited March 2023

    Yes leaving the orifice off makes it be about the same as a D which is about the same as a #1 main vent, about the same for either Jacobus or Gorton.

    it will work the same, there is no brains in the orifice

    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el
  • Mad Dog_2
    Mad Dog_2 Member Posts: 7,109

    Gorton or Hoffman. Mad Dog

  • KC_Jones
    KC_Jones Member Posts: 5,742

    The question that pops into my head is why you need to vent so many radiators so aggressively? It sounds like a lack of main venting.

    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
    ethicalpaulMad Dog_2
  • Tuggy
    Tuggy Member Posts: 46
    edited March 2023

    Yes, there is a lack of main venting imo. The thermostat for the 3 story house is on the 2nd fl, in the adjacent dining room before the living room (end of the run. Layout of each fl is the same.) The two rooms are connected by a large open arch, not a simple tiny doorway. The vertical riser that serves the 3rd fl has been tapped with a MoM D capped angle vent as well to "bolster" the 3rd fl Living Room.

    Despite that, with the thermostat set at 75° during the day time, the Living Room(s) generally reach 72° while the Dining Room(s) do get to 75°. As you traverse toward the rooms at the oppostie end of the house, the disparity climbs to be as much as 4° higher than the thermostat setting, up to 79° at times.

    A 45 ft run serves the front end of the house we're discussing here, with a Gorton No. 1 on there.

    This is nearly up against the wall at the end of the run, so I used a mirror to get the shot, and processed it using a mirror or "flip image" tool.

    There's not much more room above, so a Gorton No 2 would require breaking of the ceiling a bit to allow space.

    A big mouth I suppose would require the same plus a several inch elbow and "shunt" pipe be connected first, if I am correct.

    1. This is a family house and I am not the final arbiter of what (larger) changes can be made
    2. I'm not sure how long this Gorton 1 has been up there. I am somewhat concerned attempting to remove it could possibly break it, requiring skills beyond my ability to reapair. I don't know how likely that scenario typically is. It does look to be in good condition and not too old from the condition of the tape around the threads.. Opinions?
    3. As far as putting something like a Big Mouth on there, I've not done this type of piping work before. Idk if teflon tape is enough on the "extension" pipe joins, or if pipe dope would be required, or some other technique. Maybe someone can enlighten me. It don't think it's that complicated a job though.

    (I should make a separate thread for this really)

    (I've made this a separate therad here: