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Main vent location

Jim_64Jim_64 Posts: 253Member
After reading through many different sources, I am now confused as to where the exact location the main vent is supposed to go.

I drew a simple diagram and I need someone to clarify whether A or B or both on the diagram is the appropriate location for main vent.

I believe I have a dry return because the return line is above the water level gauge on the boiler.


  • Bill_110Bill_110 Posts: 52Member

    That is a good question. While most sources indicate B as the position and I suspect this is about where it is on most systems, I think I've also read in Dan's book somewhere and in some other sources that A position, that is after the last riser, would actually be the better position. There are no more radiators to heat after this point, so it becomes a waste of evergy to push the air out of the rest of the piping with steam. I would like to hear a more definitive pronouncement from an expert on this point.
  • Supply House RickSupply House Rick Posts: 1,404Member
    my vote for \"B\"

    i have always thought the very end of the dry return to be better, so as to remove all the air even though it is after the last riser. the left over air could expand when the system goes to vacuum at the end of the burn, and impede the flow of condensate back to the boiler. if you had a counterflow system you could only use "A".--nbc
  • Jim_64Jim_64 Posts: 253Member
    A or B or both

    Any other experts here that can shed some light on this issue?

    According to the link below, it seems like the correct location for main vent in one-pipe system is at the end of return 15 inches from the end where it drops to wet return. Is this the right way?
  • Mark Z_2Mark Z_2 Posts: 24Member
    Main vent location

    Pin, not an expert, but did expand my 1 pipe steam system on my own w/ help from Dan H's book, research, the venting guide sold on this web site, plus some help from the great people who visit and comment on the Wall. My recommendation for a main line 40' and plus is to start w/ vent A with 2-#2 Gortons, do the open port vs. w/ vents time study to verify total vent rate required and the justification for the 2- #2 Gortons. However, w/ a dry return I do agree w/ nbc about the potential for a vacuum induced pull back on the condensate. Add another vent at B as a back up, maybe a Gorton #1 (pex supply had best prices that I found). Air is always the enemy and must be chased away like a racoon from the garbage. Best of luck.

    regards, Mark Z
  • Supply House RickSupply House Rick Posts: 1,404Member
    the quote of the year!

    what a wonderful simile!!!!!!!!!!

    Air is always the enemy and must be chased away like a racoon from the garbage.
  • get the books

    Get the " steamy deal books" from this site and you'lll have all the answers, if not, you are welcome to ask more here.
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