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Steam boiler repair

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I’m helping

out a friend of mine, and need some advice.


The boiler

in question is a Weil-Mclain cast iron steam boiler, about 15 years old.  Overall, it is in fine shape, but the sealant

has come out between two of the boiler sections.  The sealant has

fallen out of one seam in the back of the boiler, and it’s leaking exhaust.  The gap at its widest is about 1/8”.  In any case, I’m thinking this can be fixed

with an appropriate sealant rather than tossing the whole boiler (the treatment

of choice by local plumbers).  I don't work with steam boilers very often, which is why I'm here.  Has anyone had the joy of doing any similar repair?  The HO would be very happy if she can get a few more years out of this one.

Peter G. Engle, PE

Almost Home, Inc.



  • More Info Please

    Hi Pete-

        Perhaps if you can supply a bit more info it might help.  What is the Weil- McLain model number and what do you think caused the problem?  Do you think the boiler ran out of water and overheated?
  • Steamhead
    Steamhead Member Posts: 16,832
    edited October 2009

    some Kaowool rope. For a small crack like you have, you may have to unravel the strands of a larger rope to get something that will fit. Tap the rope into the crack from the outside with a putty knife until you have at least two layers in each crack. Then cover it with red hi-temp silicone.

    Is this a pressure-fired boiler?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Pete_Engle
    Pete_Engle Member Posts: 7
    Right answer

    That's pretty close to what I expected.  I was going to use rock wool, but that's because I wasn't even thinking about kaowool.  Thanks. 

    And, no - it's not pressure-fired, but there's just enough pressure variation in the combustion chamber that exhaust puffs through the gap.  The burners are burning clean, less than 10 ppm CO in the exhaust, so nobody's noticed the leakage until now.  The HO said that she occasionally saw a puff of "steam" near the exhaust pipe, and that's why the local plumber immediately told her she needs a new boiler.  Of course he also told her it could blow up her house........
    Peter G. Engle, PE

    Almost Home, Inc.

This discussion has been closed.