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Update plus question

I've been ill the last few weeks and haven't been doing to much work at home but i've gotten back on my feet and continued the exploration to this issue. So the leaking issue is resolved. The thermostat wasn't shutting off when it reached the temp so it was continuously heating and heating and eventually started spitting water. I replaced it with a non programmable one and the hissing stopped. I also added 3 #4 maid o mist vents to 3/5 1st floor radiators and a C maid o mist to 1/2 2nd floor radiators. No more hissing no more water. But now i'm having a second issue. The water in my boiler has slowly been disappearing over the course of the week. The boiler has been off so i can't seem to find where the water could be. Looking for a guide to start looking. Thank you 


  • Jamie Hall
    Jamie Hall Member Posts: 20,462
    Two possible places -- any wet returns (any pipe below the boiler water line) or the boiler itself. Since -- hopefully -- there is a Hartford Loop, it's easy to start at least to find a slow leak.

    Pick a warm day...

    Turn the boiler off and drain the water out enough to be below the bottom of the Hartford Lopp. Mark the sight glass and wait patiently. If the water level doesn't drop, there isn't a leak in the lower (water) half of the boiler. If it does, there is,,,

    Now fill the boiler back up to the top of the Hartford Loop and again mark and wait patiently. If the water level drops, the leak is almost certainly in the wet return piping somewhere (there is the rare odd instance of a leak in the boiler right at the Hartford Loop elevation, but that's a somewhat less likely).

    Now if you haven't found it yet with the boiler off, fire it up again and let it run. If the water level drops enough to add more than a gallon a week, you still have a leak -- but it may be from losing steam somewhere, which can be very hard to track down.

    There is always the possibility of a leak in the boiler above the water line. The best way to find that is to again turn the boiler off and fill it high enough so that the water is in the risers (don't go above that) just above the boiler. Usually leaks above the water line are big enough so the water level will drop back down within a day or less and also usually you will see evidence of the leak on the floor (you won't when the boiler is running -- it will be steam you are losing, and you likely won't see that).
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England