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Are looped mains necessary?

car3 Member Posts: 10
I have 3 steam mains that are pitched away from the header and go to different areas of the house. They then drop and return to the boiler well below the water line. This is a two pipe system. The radiator returns return back to the boiler with a separate pipe. Can I place a thermostatic trap at the far end of the mains so I don't need to run steam in the return portion of the main?


  • Rod
    Rod Posts: 2,067
    Main Return

    Hi-  The simple answer is, yes you can, but it should be working well the way it is. Are you having a problem with the system? Putting in a trap may slow down the venting.. Where are your main vents located now?  (See attached diagram)

    - Rod
  • Jamie Hall
    Jamie Hall Member Posts: 22,877
    How's that again?

    If the mains at the ends drop down to well below the water line, they are dropping into a wet return, and there shouldn't be any steam in there at all.  You don't need a trap; the water seal does the job just fine.  A trap would just get in the way and add one more thing to maintain.

    Am I missing something, or not understanding your set up?

    You do need vents at the ends of the mains before they drop down, though, unless you also have dry returns and there are crossover traps into the dry returns.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • car3
    car3 Member Posts: 10
    Looking for ways to save $$$$

    The hot returns come most of the way back - 15 ft, 15 ft, 20ft of 1 1/2" pipe - before dropping down below the water line. Is that a lot of steam to make to fill those pipes? I have added vents to the ends of the mains and switched to a vaporstat from a pressure trol. The system now runs of less than 1psi. Just looking to save some on the fuel bill
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,487
    Adding traps will add problems.

    You don't need them on this system and adding them won't save money. Jamie is right. 
    Retired and loving it.
  • Rod
    Rod Posts: 2,067

    If your vents are on the end of the steam mains just past the last radiator lateral it shouldn't make a difference. The heat you are experiencing would be from returning condensate,not from steam as past the Main vents air is trapped between the vent and the water seal in the wet return.so steam can't enter that part of the return. I'd stick with what you have.

    If you want to make your two pipe system more efficient I would look into orifices.

    Use the Search the Wall button at the beginning of the posts and use the word  orifices and Henry Gifford , There has been a lot of good discussion on orifices lately which might be of interest to you,
  • car3
    car3 Member Posts: 10
    Thanks. I will leave them alone

    Ok. The pipes are insulated so I will leave them alone. It just seems like there is extra piping on my system with the hot returns as I have separate dry returns from the radiators taking the condensate back to the boiler. I attached a picture showing one of the loops. This one vents throught a t trap close to the boiler.
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,314
    What are they insulated with?

    black foam is not very good on steam lines. 1" thick fiberglass would work much better.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
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