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glass sight not bobbing up and down

Thank you in advance for your help.  Last night I was filling my old oil steam furnace

and accidentally left it on for to long and over filled it.  I drained out the extra water ( about a

little more then one bucket) in till it was at the correct amount on the glass

sight.  Now I noticed that when the furnace

turns on to heat the water the water in the sight glass does not bobbing up and

down as it use to, now it just stays at the same spot.  The furnace seams to be working it turns on

and heats the water but I am just concerned that there may be a problem since

it does not bob up and down like it use to. 

Any help would be appreciated since I have my 1 year old daughter in the

house and don’t want any thing to happen. 

I have no clue what I am doing so for all I know this may be normal until

all the water is heated up again.     


  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    Site glass steady

    Is there a drainable low water cut off on your boiler? If there is one, then the valve can be opened to flush out the float valve chamber, and the waterline in the sight-glass should go down. When the valve is closed, then the waterline should rise up to its normal level.

    Have you had your yearly boiler service this year? If not, it may be time to do so!

    Some steam books from the shop here would increase your knowledge of these wonderful systems, and enable you to diagnose many, and repair some faults yourself.

    A properly maintained boiler should not have an over active waterline in the glass.--NBC
  • ChrisN711
    ChrisN711 Member Posts: 4

    I am not sure I fill it my self and filled it up too much.  I already drained it and the water line is where it should be but it does not bobb up and down like it did before this mistake by me.  
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    Global warming?

    Are you somewhere very cold? Today in Nebraska it will probably be 100deg!, and maybe 76 at night!--NBC
  • ChrisN711
    ChrisN711 Member Posts: 4
    not cold

    No not cold but the furnace heats my water, so right now it only turns on for that.  
  • Patrick_North
    Patrick_North Member Posts: 249
    Steady is good!

    As Nicolas mentioned, a steady waterline in a steam boiler is a good thing! It suggests (among other things) that the water is free from oil and other contaminants that would cause a jumpy, erratic waterline. If you drained and refilled with fresh water you may have inadvertently cleaned the boiler somewhat.

    Did you fire the boiler long enough for it to create steam? If not, you could also expect your waterline to remain very still. A side note- when adding water to a boiler it's best to boil it soon after to drive off the (corrosive) dissolved oxygen in the fresh water. Usually not much of an issue during the heating season when the boiler is running regularly, but with a few months of warmer weather to go you might want bring your steamer up to a boil.

    If you're looking to educate yourself, a book available from this site "We Got Steam Heat" is indispensable for homeowners. Just saw that it's on sale:


    Worth its weight in gold- you'll save money, avoid getting burned by contractors, and you'll sleep better!

    Good luck,

  • ChrisN711
    ChrisN711 Member Posts: 4
    Thank you everyone!!

    Thank you for your help with this issue.  I was not sure if I broke something or not.  My wife will be glad to hear its ok and I am glad as well because now she can stop yelling that I broke it lol.  Thanks again!! and I will be buying that book!!!  
  • Paul48
    Paul48 Member Posts: 4,469

    It may be an indication that you are not blowing the boiler down frequently enough. That's exactly what you would hope the system would do.
This discussion has been closed.