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Sight glass water disappears daily

We need to fill the boiler's sight glass with water on a daily basis. Would you suggest an automatic water feeder, a low water control, interrupter, all 3, or something else? The boiler is 30 years old. I don't see any leaks at the base of the boiler. Thank you for your help!!!!


  • KC_Jones
    KC_Jones Member Posts: 5,737
    I would suggest you find the leak.

    Have you tried shutting down the boiler and overfilling to the header to see if you have a leak?

    An auto water feeder isn't the solution for excessive make up water.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • Mike1776
    Mike1776 Member Posts: 3
    Thank you KC Jones ! (Celtic fan?). Will do.
  • Gsmith
    Gsmith Member Posts: 431
    If it's steam, check all radiator valves and vents for steam leaks, check main vents for leak when steam is present, and check wet returns for leaks. Fill boiler as @KC_Jones said, and if all fails, look outside at your chimney when the boiler is running to see if there is a plume of white smoke (actually steam) coming from the chimney.
    JUGHNE Member Posts: 11,061
    Overfill when cold as KC suggests.
    Do you have any return pipes under the floor or that you can't see?
    Steam leaving the chimney is a bad sign.

    If you need a boiler replacement.....it is highly suggested to come here for advice before hiring someone.
  • Mike1776
    Mike1776 Member Posts: 3
    The oil company said that the problem has to do with the radiators which hiss when the heat is coming up. The oil company said that a great deal of water is being lost from the radiators, and to call a plumber. Does this make sense?

    thank you
  • Grallert
    Grallert Member Posts: 644
    If the hissing stops when the radiator heats up than it's likely not the vents. Try putting a cold spoon up to the orifice on the vent/vents, if you get condensation/water on the spoon it's likely the vent/vent are not closing and you're loosing water there. Your valves are another like culprit. Look for signs of water, you can do the cold spoon thing there as well. start working your way back to the boiler. In fact you can use a variant of the cold spoon trick in the flue of the boiler after it's been running at steam. If it comes back wet than let it cool and flood it looking for drips. Fingers crossed on a bunch of loose packing nuts at the radiator valves.
    Miss Hall's School service mechanic, greenhouse manager,teacher and dog walker
  • Fred
    Fred Member Posts: 8,542
    That much water, daily suggest a bigger leak than hissing vents. Are any of the wet returns running back to the boiler under the basement floor? They may be leaking. Does the boiler shut down when you have to add water? If the glass is empty or near empty and the boiler still runs, you need to have the Low water Cut-off checked, especially with this much water loss.
  • Jamie Hall
    Jamie Hall Member Posts: 23,280
    One thing you said worries me badly. You enquired if you needed a low water cutoff control. Ah... yes. In fact, if you don't have one and are losing that much water, I'd shut the thing off and run it only if someone is actually there, watching it all the time, until you can get one installed. And I do mean all the time: if the burner is running, the watch person is there. No potty breaks. No computer time. No cellphone. They have just the one job.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • New England SteamWorks
    With that much water loss you either have underground leaking returns (unusual in residential), or your boiler has corroded above the water line (the leak is in the form of steam going up the chimney) and needs replacement.

    Before considering replacement, study here long and hard. You'll soon learn why...
    New England SteamWorks
    Service, Installation, & Restoration of Steam Heating Systems