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Single-Pipe Radiator Central Vent Line Vents?

Harry_6 Member Posts: 141
I can't remember what it is called, but you know those systems where each single-pipe radiator has a thermostatic vent which connects to a central 1/4" vent line - often with a vacuum pump at the end? There used to be replacements made by one of the manufacturers for those vents - Hoffman or Dunham, I think. Now I know almost no one uses those systems anymore, but this same tiny trap/vent was used as a crossover vent by Dunham. Since it's easier to replace with the same thing, if possible, I'm wondering if anyone knows if those are still made? I don't know what they are called, so It's hard to look them up. If not, I'll just adapt for regular 1/2" traps, but I am curious.


  • Steamhead
    Steamhead Member Posts: 16,842
    You're thinking of the Paul and similar air-line systems. ISTR Hoffman made the #3 vent for these systems, but have not seen one in a long time.

    I've seen a couple of these Dunham setups too- they bushed down tees in the mains to use these 1/4" vents. If yours is similar, get the bushings out (might need an impact wrench) and put in Big Mouth crossovers. This will radically speed up the venting process.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Harry_6
    Harry_6 Member Posts: 141
    Thanks for the reminder: Paul system (the Dunham version). I'm hoping I can do something like what you suggest, if logistics permit. They came off the main at 1/4" to the trap, then increased to 3/8" to travel another 4' into the dry return. I'll have to see what I can manage. Thanks again, and Happy New Year!