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Red or Brown stains on Chimneys

Howard_9 Member Posts: 1
My concern is what is causing chimney staining from the flue outlet down. It is a reddish brown stain. Our company is located in the northeast section of the country. A local Chimney Contractor claims that it could be the red dye in the #2 fuel oil or unburned carbon. The internet is no help. The staining is not as noticeable on brick or stone chimneys but it is on painted stucco ones and especially ranch homes where the chimney goes through the center of the house and it stains the shingles. It appears all have chimney hats and or have been lined and hatted. I cannot find anything specific on this subject and the two camps ; red dye or unburned carbon have made anything definitive.

Does anyone out there have anything definitive???


  • njtommy
    njtommy Member Posts: 1,105
    edited September 2016
    Just a really silly question, but what type of cap do you have on your chimney? Is it stainless steel or just a black cap?
    If it's just a black cap the powder coat starts to flake off and then exposes the steel they use to make the caps. once that starts to rust Every time it rains it will run down the chimney and cause rust pots.

    Also posting pictures is a big help. I can ask my Dad he use to be a chimney sweep for 20 plus years.
    Erin Holohan Haskell
  • STEVEusaPA
    STEVEusaPA Member Posts: 5,687
    It's most likely condensation from low flue temps. The carbonic acid is eating away at your chimney.
    The dye has nothing to do with it.
    Is this a new problem, new equipment? What are you stack and net stack temperatures, measure with your combustion meter, and your over fire and breach draft.
  • captainco
    captainco Member Posts: 592
    Sulphur in the oil can cause the reddish brown stains. But where it is occurring indicates the flue gases are condensing so there is some kind of a venting problem, such as low flue temps, excess negative pressure in the mechanical room.
  • ChrisJ
    ChrisJ Member Posts: 12,810
    Sounds like a good application for an insulated liner of the proper size for the connected appliance(s), no?
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment