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New Steam Main Layout

I'm adding a third steam main to an existing one pipe system. The new 2" parallel flow main will go around this section of basement in a U-shape and turn to a 1.25" return. Radiator run-outs will also be 1.25"
Given the 2" main will be 12-14" below the finished floor, how far in from the outside wall should I run the main? I'm thinking 2 to 3 feet away but that is just a hunch. Any suggestions, guidelines, or rule of thumb?


  • Jamie Hall
    Jamie Hall Member Posts: 21,524
    I can't think why there'd be a restriction, other than custom or convenience for swinging wrenches...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    JUGHNE Member Posts: 10,786
    Because the runouts are counter flow there is a limit to the horizontal length.
    2-3' should be good for most, from what I have seen.
    There are steam piping charts for this.

    Have you considered making this main a 2 pipe system?
    EBEBRATT-Ed Member Posts: 13,776
    And does you boiler have the capacity for the added radiation?
  • dennis53
    dennis53 Member Posts: 57
    Thank you for all the comments. I've considered making it 2 pipe, but trying to keep it simple without traps, orifices, or water seals. The boiler does have the capacity, but will be cutting into the pick-up factor a bit. Thanks again,
    JUGHNE Member Posts: 10,786
    Two pipe would give you smaller run outs. Smaller pipe to deal with.
    No rad vents.
    Smaller supply valves with some adjustment possible at each rad.

    You will need a water seal at EOM with 1 pipe or F&T trap to dry return.
    Steam main air vents in either system.
    STEAM DOCTOR Member Posts: 1,785
    You can also use a separate return main with wet returns for the supply and return mains.