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Water Leaking from Glass Tube

Jeanne S.Jeanne S. Member Posts: 7

I have a steam furnace, from the 1940's I believe that has been updated, I am having leakage from the glass tube, appears to be condensation and water coming out. I tried to tighten the valves on each end but it is still leaking when it gets very heated up. Not a ton of water, but enough to be a concern? I would really appreciate any input. Thanks so much, Sandi


  • nicholas bonham-carternicholas bonham-carter Member Posts: 6,540
    leaking sight glass

    i doubt that condensation could be causing moisture to form on the sight-glass on your BOILER. from time to time, the rubber washers on the top and bottom of the glass tube will get hard and leak. however the cure is to close both valves [gauge-cocks] and unscrew the nuts holding them in place. the tube can then be removed and new washers put on. however, you say that you have closed the gauge-cocks and still it leaks. that would make the changing of the washers a job for a pro, and should include replacing the gauge-cocks as well. those gauge-cocks should be left open so that the water level can be seen. if you have to operate like this, then be absolutely certain that your low water cut off is working! some times the nuts can be tightened, to stop the leaking, but there is a risk of breaking the tube, and if your gauge-cocks don't work, you will have no water in the boiler, only on the floor!

    post a picture of the leak and maybe there is some other solution.nbc
  • Jeanne S.Jeanne S. Member Posts: 7
    Water Leaking From Glass Tube

    Thank you for the information, it only happens when the furnace is getting very heated....when it has to heat up alot..some of it is just trickling out. I will try to get a picture of it today. I just wondered if it didn't need to just be tightened up? I didn't want to call someone if it was just a simple turn of a wrench. I really appreciate the input. Thank you, Sandi
  • ed wallaceed wallace Member Posts: 1,613
    leaking sight glass

    the sight glass and rubber gasket will have to be replaced staem wears out the glass and dries out the rubber gasket
  • nicholas bonham-carternicholas bonham-carter Member Posts: 6,540
    sight-glass leaking

    if you have a pro help you with this, have him check the pressure on your system, as the increase of the leak while "heating up" may indicate over-pressure. it should be as low as it can go-under 1 psi is ideal.--nbc
  • ErichErich Member Posts: 135
    Not a Furnace

    You do not have a furnace. A furnace is a hot air heater. You have a steam boiler. Please post the make and model of your boiler. Is it gas or oil fired. What is the pressure gauge reading and what are the pressure set points? Pictures would be even better.
  • nicholas bonham-carternicholas bonham-carter Member Posts: 6,540
    unmentionable word

    sandi- we're all boiler people here, please do not use the F-word [furnace]--nbc
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