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

main vents can this work?

Hollis Member Posts: 105
From what I can tell,I could use more venting from my mains,..it would be hard to tee off and put more on where they are now. Not sure of the brand but they are "bullet" shaped and as I understand it they work to close when they reach a certain temp and it does look like they still do that well. However they have a very tiny hole in which to vent. can they be (carefully drilled out to have a larger orifice? (as long as the drill doesn't go in to damage the innards)

BTW the hole is 5/64,...as a main vent,.why would it be so small? would it be OK to drill it out to 1/8 or larger?

2nd question,..I tried to remove them,...very hard,..can I spray them with "blaster" or any other penetrating oil w/o contaminating the water/steam?


  • Steamhead
    Steamhead Member Posts: 16,889
    Wouldn't work

    the pin that closes the hole is only that size. If you drilled it out, it would never close.

    There are several techniques for getting those vents out. Penetrating oil, heat from a torch (be VERY careful if you use this method, to avoid starting a fire), cheater bars etc. But it might be best to call a pro.

    How long are your steam mains, and what pipe size are they?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Hollis
    Hollis Member Posts: 105
    Thank you steamhead,..the hole

    is on the side,.(NEAR but not on the top ,...I believe its a Dole) , thats why I thought the mechanism to close the valve was more internal and the orifice of the outer casing was the limiting factor in the venting. (?)

    Re pipe size,..you mean the size to the main vents?
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,846
    edited February 2012

    The opening you see isn't the actual vent port. When you find a vent that isn't venting at its full capacity due to the buildup of scale you usually won't actually see anything obstructing that hole, and even if you do, clearing it won't help, because the real obstruction is inside.

    Re. size, yes, the size (length and pipe size) to the vent. He needs that to calculate the volume of air that needs to be vented through that vent. If there is more pipe after the main vent it doesn't matter unless there's another radiator connected. The main vents should always be connected after the last runout or riser comes off.
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • Hollis
    Hollis Member Posts: 105

    Thank you also. Its my rental house aways from here so I will have to measure later.

    One other question I always wondered,..how are these main valves any different than a regular radiator steam valve,..essentially don't they do the same thing? The capacity to vent the whole system quickly? But how can they do that (in this case) with such small vent holes as opposed to a quick (say an open varivalve) radiator valve. is it a vacuum thing?

    I don't intend on doing any replacing with one t as I suppose there is a reason that fact that main valves exist but always wonder what is the difference?
  • Dave in QCA
    Dave in QCA Member Posts: 1,786
    Will Work

    I have used a Heat Timer Varivalve as a riser vent, and have also installed them as a main vent in a pinch.  The thing about the Varivalve is that they have a reputation of not being very durable.  They also sometimes spit out a dribble to two, of course this isn't a concern in a basement.  Also, they do NOT have a float and so they do not close against water.  Hoffman and Gorton vents to have floats, but the reliability is marginal.

    At 1 oz of pressure, A straight pattern varivalve will vent at 0.66 cfm., a Hoffman #75 will vent at 0.50 cfm, a Gorton #1 will vent at 0.330 cfm., a Gorton #2 will vent at 1.10 cfm., an open 1/8" pipe will vent at 1.20 cfm, and an open 1/2" pipe will vent at 2.60 cfm
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
This discussion has been closed.