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Leaking cast iron boiler

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  • Leak in old cast iron boiler--what to do?


    After tinkering with the 1950's radiant heating system in my mother's house for some time, I finally got all the air out of the system (in the process getting heat to several rooms that hadn't been warm in years) and got everything balanced. I also rearranged the piping around the 1953 Capitol Gas Boiler so I'm pumping away from the expansion tank, replaced it with a diaphragm tank, and replaced the air separator (the original one wasn't installed properly), relief, and fill valves. I was really pleased with myself. Now, after running at the correct pressure (it's 10.5 psi instead of the 5 that it had been running at for years) for a few days, I find that the boiler is leaking from the section next to the end section with the inlet/outlet. With the boiler off I pulled off the back panel and there is a pile of (I assume) rusty debris about 3/4" thick on the floor. The leak is enough to make a good divot in the rust pile. The location is very near the cold water return near the lower water passage (inlet). There is an embossed label on the boiler saying "DO NOT EXCEED 120 DEGREES", probably placed there by my grandfather. From what I have read I believe that the boiler has been "rotted" by condensate. I calculate approximately 50 gallons of water in the system, and the pressure drops two PSI or so every day unless I open the fill valve.

    Question: Can we nurse this thing along until the end of the heating season (mid-March) when we can afford to replace it? Will adding hard northern Illinois water every day destroy the copper loops in the ceiling or will the minerals be deposited in the boiler? The burners appear clean, but are there any additional safety hazards we should be aware of? The boiler is in the basement--below all the radiant loops.

    I know that the easy answer at this point is to "hire a professional". However, various professionals in this area were hired over the past 15 years to fix this thing and have not been able to. Nor did the last one notice the foot long hole in the water heater flue that runs over the boiler, which nearly gave me a heart attack. I am a mechanical engineer with a great deal of hands-on experience (do all my own auto repairs, have my own machine shop, have designed and built many houses, do electronics work, have designed control systems, etc.). I'd like to do the replacement myself (with the exception of the gas line work), but can't until later in the year because I live on the East Coast.

    Any advice is most welcome.

    Jonathan Stevens
    Rockford, IL (until Jan 7)
  • Al Corelli_2
    Al Corelli_2 Member Posts: 395
    Al Corelli, NY

  • some may gasp

    at this suggestion, but, if you're seriously considering the replacement of that dinosaur and hoping to simply nurse it throuhg the season, a boiler stop-leak product may be the answer. it worked for me
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928

    Your best bet to "nurse the boiler along" for the rest of the season may well be to lower the pressure. You said the system had been running at 5 psi for years. Is it safe to assume that it held this pressure without adding water? If so, 5 psi will raise water about 11.5 feet. Unless your basement ceiling is extremely high or you're heating more than one story, 5 psi will be adequate.

    If your circulator is pumping away from the point of no pressure change (the expansion tank connection), then it's impossible for the circulator to contribute to "air problems" as it can only add to the static pressure.

    54 years for a boiler sounds to me like a very acceptable service life. The low operating temperatures possibly--but not definitely--could have caused some condensation damage. Has the boiler flue piping been replaced a number of times?
  • leaker

    Thanks for the replies. As far as the 5 psi goes, I suspect that it would have held pressure before but not after my repiping, bleeding, etc. If I lower the pressure back to 5 psi there will be two levels of ceilings that won't get circulation, and I'm afraid of freezing in one of the coils (this happened a few years ago before I added insulation). The house is a split level but with 5 levels, so it's really 2-1/2 stories.

    I don't know when or if the flue pipe has been replaced; certainly not in the last decade. The flue pipe that is there now is in good shape according to my knuckle-rapping test.

    Personally, I'm rather attached to the old dinosaur (it's actually 57 years old, apparently), but I agree that it would be insane to try to repair it. Leak-stop is not a bad idea if I can figure out a way to get it in there without contaminating the radiant loops.

    Jonathan Stevens
    Rockford, IL (until Jan. 7)
  • Al Corelli_2
    Al Corelli_2 Member Posts: 395
    Leak Stop

    I would not want that leak stop material in the radiant loops.

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
    Al Corelli, NY

  • in the loops?

    from my understanding of it's usage, it's a physical blockage of the leak by the once suspended particles, and only settles at the leak site. and if you're going to end the nostalgia at some point in the near future, flushing the complete system will flush out the remainder of it.
    but, if you don't want to put 'ol bessie down, and if it's a sectional boiler, you could simply replace the leaking section when the time comes
  • Al Corelli_2
    Al Corelli_2 Member Posts: 395
    yes, in the loops

    As pretty as the manufacturers of leak stop like to paint the picture of it only adhering to the leak areas, in my experience, that stuff coats the inside of darn near everything. I would not want a layer of ANYTHING between my heating fluid and the tubing. And, yes I understand that there is probably years of "film" built up on the tubing. I feel there is no reason to add to it.

    Where do you get sections for that 1953 Capitol boiler? :)

    I would agree with you if the boiler could be isolated, sealed ,flushed then put back into service, but before doing all that work, we are better off installing a new boiler. Money better spent, in my opinion.

    Happy New Year

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
    Al Corelli, NY

  • sections for a '53 capitol boiler?

    i don't know, and that's why i suggested replacing the boiler, but he said he was sentimental about the '53

  • I was joking about that part (it's just that it's been in the family so long). The problem is that it is leaking about a gallon a day as near as I can tell and we really need it to hang in there for about two more months.

    Jonathan Stevens
This discussion has been closed.


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