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What brand of main vent is this?

Has anyone ever seen one of these before? I'm not sure it's working right. It never seems to vent and I'm wondering if I should try and clean or replace it. My system has two of these, one on the end of each steam main. The only identifying mark on it is "#4" which I assume is the vent size.


  • Old (Hoffman?) main vent

    When the boiler is starting to make steam, and the air is starting to be pushed out, hold a tissue over the vent hole, and see if it is working, by checking for air movement

    I suspect it is not, and should be replaced with a gorton 2 on each main.

    If the tapping is at the very end of the main, use a couple of 90deg l'sin the form of an antler to protect it from any water-hammered slugs of water coming up the wet return.

    You can never have too much main venting.--NBC
  • pcloadletterpcloadletter Member Posts: 38
    edited December 2012
    It looks the most like a Dole #4.

    I tried the tissue method and it didn't indicate air movement from either of the two vents. One made a faint whistling noise for a few minutes but that's about it.

    I'm considering replacing each main vent with a Gorton #1. I think a #2 would be too large. Both mains are fairly short and the house is only 1000 sqft with 6 radiators.
  • Hap_HazzardHap_Hazzard Member Posts: 1,349

    The Dole #4 and Hoffman #4 look very similar and are interchangeable, but this one looks more like the Dole. They have the same venting capacity as the Gorton #1, but they lack floats and are sensitive to water. I think you'll find that soaking them in white vinegar overnight will get rid of all the built up scale and restore them to their former glory, but make sure they close against steam. The Gorton is a better vent, and if whoever installed the #4s knew what he was doing they should work fine. If not you can always add on another. You'd need 4 #1s to get the venting capacity of the #2, so it's usually cheaper to add #1s progressively unless you're sure you need a #2.
    1983(?) Peerless G-561-W-S
    3" drop header, CG400-1090, VXT-24
  • pcloadletterpcloadletter Member Posts: 38
    Since I am short of money...

    I think I will try cleaning the existing vents first. They are both on risers which put them a couple of inches above the highest point in each main.

    As for replacing them - I know this sounds stupid, but how do I measure the length of each main? Do I just measure the horizontal section or do I measure all the way from the riser back to the Hartford loop? My mains are 2" from the header to the last radiator branch, then they reduce to 1-3/4" back to the Hartford loop.
  • Hap_HazzardHap_Hazzard Member Posts: 1,349
    The point is to measure the volume of air

    that must be vented in order to fill the main with steam, so you measure from the riser to the main vent.

    Those extensions mean that the person who installed these read the instructions. Because this vent is sensitive to water, it should be mounted on a 6—10" extension. It's not a bad idea to do this with any main vent.
    1983(?) Peerless G-561-W-S
    3" drop header, CG400-1090, VXT-24
  • pcloadletterpcloadletter Member Posts: 38
    Just installed my Gortons

    Got my Gorton 1's from PexSupply today and just installed them on the mains. We'll see how well they vent.
This discussion has been closed.


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