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White powder

I have a Weil-McLain PEG-55 natural gas fired steam boiler. It’s roughly 10 years old. I recently took the top off due to curiosity and found tons of this white powdery buildup around the combustion chamber. There is a hood that covers the clean area and the white buildup is outside of where gases are vented. The vent stack is perfectly clean. 

Thoughts appreciated!


  • gerry gill
    gerry gill Member Posts: 3,078
    Do you mean the furnace cement that the flue collector was bedded in?
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

  • Steamhead
    Steamhead Member Posts: 16,998

    Do you mean the furnace cement that the flue collector was bedded in?

    @gerry gill is right. It's old furnace cement. Clean it away and spread new furnace cement around the flue collector when you reassemble.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    Shouldn't need that much cement. Did something happen to the flue collector?

    There was an error rendering this rich post.

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,166
    The original question was about white powder around the combustion chamber. However there is no picture of a combustion chamber. The picture shows the top of the cast iron heat exchanger with very clean flue passages. There is a white powder that covers the part of the cast iron that was not covered by the flue collector box. The actual combustion chamber on this boiler is at the bottom of the cast iron heat exchanger. It is where the fire from the burner tubes is located. the chamber or area where the Fire happens, hence combustion chamber.

    Regarding the powder, if that blue sheet metal cover has never been removed until now, that white powder may have been there since the boiler was installed. Drywall dust from a construction job can find its way everywhere. Unless there was an anthrax scare at the time of the boiler install, I wouldn't worry about it.

    If it is anthrax, we may not hear from @Jcfenton87 again. Oh Well!

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    EBEBRATT-Ed Member Posts: 15,829
    look pretty normal to me
  • Jcfenton87
    Jcfenton87 Member Posts: 2
    Thank you all for your input. After taking a second look and considering your observations, I’ve determined it is furnace cement. Albeit poorly applied (IMO). We had an issue with our service provider not performing cleanings as prescribed, so this jumped out as a scare, but concluded as benign. I’ll reseal and reconnect ducting just in time for heating season! 🔥