Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

No water in sight glass + not sure if low water cut-off unit is working or not

JimmyNJ Member Posts: 107
Hi everyone,

A family friend just bought a house with steam heat and had asked me to come over to take a look because when the heat was on, one of the upstairs radiators "had steam coming out of it". It looked like the air vents are very old so it is possible that one of them have failed in the open position and does not close when the steam hits it, however, the real reason why I am posting here is that I didn't see any water in the sight glass (and family friend had run the boiler about 30 min before and the house was nice and warm), and the water cut-off system (Safegard 400SV) did not have the amber LED light on indicating low water. The sight glass knobs were completely "stuck" so while I think they are in the open position I couldn't verify. I was thinking about using PB blaster on them (where the rod goes into the nut) to try to unstuck them but wasn't sure if that was a big no-no? I am thinking that I need to solve that issue before I attempt to drain the boiler completely (too see if the low-water cut-off unit is broken or not because if the unit does work, I won't have any idea how much water to add back. Does anyone have any thoughts on how to troubleshoot this further to make sure that the boiler does not end up dry firing?


  • neilc
    neilc Member Posts: 2,700
    turn it off , , ,
    , , , until you can figure out the water level,
    and that the LWCO is functional,

    known to beat dead horses
  • SlamDunk
    SlamDunk Member Posts: 1,579
    That is the cleanest basement I have ever seen.
  • neilc
    neilc Member Posts: 2,700
    if the boiler drain is functioning,
    you could attach a short hose, like a washer machine hose or scrap,
    hold it high against the sight glass, open the drain slowly and slightly, and lower it till water is at the hose end,
    that would be a water level,
    if it's above the bottom of the sightglass, then those glass valves are either closed or plugged,
    loosen the packing nut and try opening,
    or, loosen all the way, and back out the valve stop, and poke a long thin screwdriver in to open the valve port to the boiler,
    check both lower and upper,
    if the hose water level is below the sightglass, then add water,
    I don't see any auto feed in these pictures,
    seems the homeowner needs to observe and manually fill the boiler.

    The LWCO is another more important matter here,
    and must be functional.
    once you can see water level (from above)
    with boiler on, slowly lower the water level to below the LWCO sensor port,
    the probe may need cleaning, or replacing,
    the controller may be bad,
    the wiring wrong,
    either fix it yourselves, or call a tech in,

    known to beat dead horses
    JUGHNE Member Posts: 11,058
    For the water level test with the hose, do not use the drain connection that is way down on the floor. One of the other two will work for that.
    If the boiler is cool enough that you can put your hands on the lower large return pipe you could add water, maybe the water level is just below the sight glass.
  • JimmyNJ
    JimmyNJ Member Posts: 107
    Thanks for all the input thus far. Will try the water level test tomorrow and also see about getting the sight glass valves to work properly.
  • Jamie Hall
    Jamie Hall Member Posts: 23,272
    Are you sure that sight glass is actually empty? They can be very deceptive when they are full, and I can't tell from the picture. It's possible that the boiler is overfilled -- or that the sight glass ports are plugged.

    In any event, use that hose test idea. And do not even think of running the boiler until you verify that the low water cutoff works.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • mikespipe
    mikespipe Member Posts: 36
    sometimes just opening and closing the valves on the site glass can free up a clogged port. and at the bottom of the sight glass there is a cleaning valve that is similar to a bleeding valve on a brake line if you shut the bottom valve and use a open wrench or socket to open the port any water will drain out of the sight glass. when you do this and the boiler is hot the steam should clean the glass. the water level trick was good advise as was not running the boiler until you know the low water cutoff is working.
  • mikespipe
    mikespipe Member Posts: 36
    also please insulate those risers you will save yourself a lot of money. use 1 inch fiberglass or rockwool.
  • JimmyNJ
    JimmyNJ Member Posts: 107
    To follow up.  There was not enough water in boiler.  I was able to unscrew both control rods on the sight glass and used a long skinny screwdriver to make sure there was no plugs of sediment (there was a ton of sludge ). Drained a couple of buckets, filled back up to normal operating level and then blew the sight glass down to get a bunch of sediment out of it - and then slowly as boiler was on drained water out until it didn’t  show in sight glass but low water cut off light  didn’t go on so turned off
    boiler - I’m thinking the probe is either coated with sediment /‘hard minerals and needs to
    be cleaned or the unit replaced.  The light on it briefly flashes when the emergency gas switch is turned on so it definitely has power.  Filled the unit back up to normal operating level after it had cooled down and told the homeowners that they shouldn’t have anyone turn the boiler on until they get the cut-off unit fixed or replaced -they have someone coming tomorrow.  Thanks for everyone’s input to help troubleshoot the situation. 
    JUGHNE Member Posts: 11,058
    That LWCO control is dated from 1999.
    I would recommend a new one.
  • JimmyNJ
    JimmyNJ Member Posts: 107
    Yes replacing makes the most sense.  Thanks