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Replace boiler because of rust

ilikebeans Member Posts: 5
I was told by the technician from the oil company that this boiler (the whole unit) needs to be replaced. Weil McLain p-366he-s. 

Here is a picture of the problem area:

He said steam might leak out of the rusted area on the black ribbed part and go out the exhaust instead of up into the pipe/radiators.

I'm looking for any opinions on whether the whole unit needs to be replaced. 

He said the worst-case scenario is that some water will just have to be added occasionally.

Thanks for any advice.


  • Jamie Hall
    Jamie Hall Member Posts: 18,907
    Well, the question is -- do you have to add water when it's running, and if so, how often and how much? If it ain't broke...

    As a guideline, more than a gallon a week besides the low water cutoff blowdown (if you do that) is too much and suggests a leak -- though that might not be it.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,180
    Weil McLain 66 series was replaced by the 68 series a long time ago. The 68 series was replaced by the GO series over 25 years ago.

    I'm thinking that "if it is over 40 years old, why would you want to keep it".

    On the other hand, I have had customer's boilers with that same blockage, in the flue passage cavity, tried to clean out that blockage with a "Soot Saw" tool, with only partial success, and left it there every year I tuned up and cleaned the boilers, for years. (boy was that a run on sentence, but you get the idea). There were no perceptible water leak. I believe that rust is from condensation of flue gas. It forms over a heating season and if not removed, it builds up into that crust.

    As long as there is at least 70% of that flue passage free from soot and scale in each of the flue passages, you should be fine. Just make sure you have an exhaust temperature above 350° at the boiler flue outlet, so you don't create more condensation of flue gas. As old as that boiler is, you never know what energy saving measures were done in the 1970s and 1980s. It may have been under-fired for some time over its lifetime. Back then we called it Down Firing. It was supposed to save on oil. Boilers rated for 1.25 GPH were fired as low as .75 GPH, all in order to save on oil. If the boiler does not make steam fast enough at that low firing rate, it can actually cost more to operate.

    The concept worked better on hot water boilers when looking at fuel savings. But the condensation of flue gas problem was often found too late. But it was probably time for a new boiler anyway.
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
  • ethicalpaul
    ethicalpaul Member Posts: 3,739
    Are you selling the house within 3 years? If so, replace it now with a correctly-sized and piped new boiler. You'll be able to say "it has a new boiler" and not get caught in the middle of winter with a leak.

    Does the boiler leak water if you or your plumber overfills it to a level above the boiler? If so, it already has a leak. Replace it with a correctly-sized and piped new boiler.

    Does the boiler perform well currently? Are you OK with the risk of probably-non-catastrophic failure during the cold season? If the answer to these questions is "yes" then roll the dice and let it ride. If the answer to either question is "no" then replace it now with a correctly-sized and piped new boiler.

    If any of the above questions leads you to replace it, make very sure you find a trustworthy steam contractor to properly size and pipe your new boiler. In 4 years on this size I have seen dozens of incorrectly sized and piped boilers and it's not fun for those homeowners.

    Oh and convert to natural gas if you can.
    1 pipe Peerless 63-03L in Cedar Grove, NJ, coal > oil > NG