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How critical is the distance between the Main Steam to the water line

I have measured the Single Gravity Main Steam pipe to the Normal Water line and I have 43". Is this ok?
I see from Dan book "If you have a gravity-return system the lowest, horizontal, steam-carrying pipe has to be a minimum distance above the boiler. In one-pipe steam, that distance is 28 inches.


  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,578
    What height is the end of the dry return from the water line. I think this is the "lowest steam pipe" in the system. When the boiler is firing at its maximum pressure of 1.5 psi, the water level in the wet returns will rise 1.75 inches for every ounce of pressure. If the end of the dry return and its main vent is too low, then it will become submerged with this rising water level, and cause banging, and inoperative main vents.
    The solution would be to raise the dry return, or lower the maximum pressure (which is why we like Vaporstats here). You only need a couple of ounces of pressure to get the steam throughout the system.--NBC
  • Jamie Hall
    Jamie Hall Member Posts: 23,428
    Too low would be a problem. Too high is no problem at all.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • mercedes
    mercedes Member Posts: 67

    The measurement from the ceiling to the main steam pipe is 10"
    and the boiler water line is 53" from the ceiling so the difference is 43". I am going to use a Vaporstat control. I feel relief that this is ok. Thank you for the help.


    Thank you for the help.

  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,544
    That's fine, Jamie. Make sure you have good venting if you're using a vaporstat.
    Retired and loving it.
  • mercedes
    mercedes Member Posts: 67
    Just calculated the venting using JP Freeley spreadsheet. Using Groton valves.

    Dan Leary

    sorry I was thanking Jamie and Nicholas for their help. Also thanks for the input.