Single-Pipe Radiator Central Vent Line Vents?

Harry_6

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

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.

Harry_6

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!