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makeup water automatic valve

Champ6 Member Posts: 20
First off, I am a homeowner, not a pro, so pardon me if I don't use the best terminology.
I have a 20 year old Weil Mclain boiler, which came with an automatic makeup water valve. Once a month, I drain it and it would automatically
refill up to just under 1/2 a glass. Lately, it's been slow at refilling, though I could put my finger in the opening, lift the mechanism up, and it would fill normally again. I sprayed some lubricant in there, but it made no difference.
Yesterday, I drained it, but was distracted and did not lift the mechanism, and this morning woke up to a cold house. Knowing what i do, I lifted the mechanism and the boiler filled and lit.
My question is how do service this?


  • Champ6
    Champ6 Member Posts: 20
    This is a Mcdonnel #47 valve
    JUGHNE Member Posts: 11,062
    You can search for repair parts and breakdown.
    If it is original to the boiler of 20 years it may need replacing. Has it ever been opened for cleaning?

    The very bottom has a water strainer that could be partially plugged.
    That is the simplest and cheapest part to change. (although nothing cheap about it).

    That looks old enough to be such that you cannot remove the fill cartridge without major disassembly. The round ports on the water connections indicate pre August of 1995.
    After that time they had hex ports and the cartridge could unscrew out the bottom where the strainer is.

    The large bowl could have crud built up in it that it will not drop as it should.
    Check the replacement part prices and you may be ahead to get a new one.

    M&M says to change the entire unit every 10 years, you are over double that now.
  • Jamie Hall
    Jamie Hall Member Posts: 23,324
    First off, shouldn't need to drain the boiler once a month -- just blow down that autofeeder a couple of times a month, just enough to get the muck out of it (a gallon or two).

    So -- try that first. But my guess is that the float inside is either waterlogged -- or hanging up on muck. You may be able to get it to work properly again that way, but you may also have to take it apart and clean it out -- and possibly replace the float. Whatever, make sure if you take it apart you have the necessary gaskets to put it back together!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Champ6
    Champ6 Member Posts: 20
    Thanks all, I got locked out somehow and have not been able to respond until now.

    Time flies, it's actually been 30 years since the boiler was installed, not 20! The auto-fill has never been changed or serviced, just flushed once a week. I think I said I drained the boiler, but I meant flushing this. this. I removed the low water shut-off switch, shot the mechanism with carburetor cleaner and then Tri-Flow lubricant, and all seems well.

    Now how do I isolate the float chamber to clean it? Do I need to drain the boiler for this? What about to clean the filter? There is a cartridge of some sort according to the information I found, so why do I need to change the entire thing every 10 years?
    JUGHNE Member Posts: 11,062
    You need to drain the boiler to open the chamber, there are 6 or so bolts.
    The chamber may have crud in the bottom....keeping it from going down to shut off the burner.
    The float may have water inside it....keeping it from floating up to restart burner.
    Or some combination of both is possible.

    With the old version you may have to dissemble a lot of the unit to get to the water valve.

    If you feel confident that it will shut the burner off in the condition of low water, then this would be a warm weather project. IIWM, I would open it all up and then check the prices of replacement parts versus complete new unit. Just getting the gasket surfaces clean can be a PIA.

    Why every 10 years?? Because they said so....in the rare event of a dry fire event/explosion...that suggestion would be used in the defense of the LWCO manufacture.
    Personally if opened up every few years for cleaning, and was the newer design of easy cartridge cleaning, I would go beyond the 10 years. And you are at the 30 year mark.

    Even smoke detectors have an expiration date...usually 10 years.