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Water disappearing from sight glass before boiler even turns on

bpthomasbpthomas Member Posts: 2
Hi, My thermostat is off, as we won't need heat for another few weeks. I inspected by gas powered steam boiler and tried to manually add water. I opened the valve and there was a long delay before the water level went up on the sight glass but it finally did. I came back an hour later and the water level was all the way back down. I repeated this and same thing happened. There are no visible leaks so where could the water be going? Again, this boiler isn't even on so its not steam loss. I do notice brown gunk and the within the bottom of the sight glass.


  • JUGHNEJUGHNE Member Posts: 7,198
    Do you have any wet returns....pipes under the floor?
    If so can you isolate them from the boiler with a valve?

    Pictures please if you are not sure.
  • Jamie HallJamie Hall Member Posts: 13,412
    Significant leak somewhere. If you have no wet returns, or a Hartford loop, it's got to be in the boiler. Which is not good news.
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • nicholas bonham-carternicholas bonham-carter Member Posts: 8,193
    Are you sure the boiler is empty?
    A full gauge glass can look empty!
    look for water on the floor.
    if the wet return pipes are under the floor, a leak can go unnoticed. Replacement runs can run above the floor, but well below the waterline, for ease of replacement-NBC 
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 7,315
    As others have mentioned look for wet returns ...pipes run under the cellar floor.

    If no wet returns I would take of the water gauge glass and make sure the gauge glass connections to the boiler are clear, The water level may be fooling you.
  • bpthomasbpthomas Member Posts: 2
    Thanks everyone! It does seem like I was being fooled by inaccurate sight glass. I took it apart and flushed out all the liquid rust and things seem to be working now.
  • JUGHNEJUGHNE Member Posts: 7,198
    Did you clean the pigtail also.....
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