Can I use single wall black pipe to gain draft height?

smit.etja Posted By smit.etja, Feb 11, 2019 at 2:22 PM

  1. smit.etja

    smit.etja
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    Feb 11, 2019
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    Installing a new but old wood stove which recommends a chimney height of 6" x 16'. My predicted setup will be 5' of black single wall pipe followed by 6' of double wall stainless steel. The 6' of DW meets the 3/2/10 guideline so I'm good on code. However, I'll be about 5' short (5' + 6' = 11') of the 16' recommend height.

    Can I install 5' of black single wall pipe on top of the double wall stainless pipe? I live in Rock Springs, WY which is high desert country. Dry, snow would never reach the black pipe, rains infrequently and very little. I work in metal fabrication so making a secure connection between the two isn't an issue. I'm looking more for reasons why not to have single wall on top of the double. Basically trying to avoid the additionally $140 to continue with double wall vs. the $15 it'll cost with single.

    Thanks!
     
  2. Jan Pijpelink

    Jan Pijpelink
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    My thoughts would be that the single pipe on top of the double wall would cool down too fast which will create a lot of creosote with the chance of a chimney fire. I also think it is not up to code. The top of the chimney is the coolest part so you want to keep that as warm/hot as possible. So double wall all the way to the chimney cap.
     
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  3. begreen

    begreen
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    Besides being against code, creosote buildup and corrosion (from the inside out) are two big concerns with reduced draft due to a colder flue also possible. The chimney is infrastructure and should be properly done to perform well under a variety of weather conditions. Do it right and be sure to brace the chimney at 5ft above where it penetrates the roof.
     
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  4. smit.etja

    smit.etja
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    Thank you both for your reply. I by no means want this to sound like an argument, hard to do in text only, but what code is this pertaining to? Is it a coupling code, exterior requirement code, ect? Wanting enlightenment on this not argument..

    I know they make double wall black pipe which is basically black Class B vent, would that be something to consider? It's just an air gap vs insulation but since Class B vent is sufficient for "hot air" rising in a furnace application, would DW black pipe be sufficient above DW insulated or is the primary concern the creosote buildup?

    Thank you again guys!
     
  5. begreen

    begreen
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    Double-wall stove pipe is not acceptable either. It needs to be chimney pipe that is class A, HT 2100 rated. A furnace pipe does not have nearly the temperature requirements as a wood stove does.
     
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  6. smit.etja

    smit.etja
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    Feb 11, 2019
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    Thanks again begreen. Is the code requirement something like "All pipe through unconditioned or combustible space must be double or triple wall insulated?" My thought being if single or double wall black pipe is acceptable right off the back of the stove, it shouldn't be a temperature requirement being that the flue temperature only decrease further from the stove origin. So in my head I see the highest temp being at the stove, decreasing through my single wall in the interior, slightly decreasing through the double wall insulated through my attic and exterior, and then exiting the cap. If I added any pipe rated to "right off the stove" to the top of the already to code stack, I don't see it as a temperature issue.

    Again, not trying to argue just want my own curiosity answered. I appreciate your time!
     
  7. fbelec

    fbelec
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    just for the reason that it would cool so much that you would have a creosote blockage and that a fire maybe after or before should do it for me.
     
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  8. maple1

    maple1
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    The main point is it's a cold temperature issue, not a hot temperature issue. If gasses keeps going up and then hit simple stove pipe, even double wall, it will cool a whole lot & make creosote. All kinds of it.
     
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  9. begreen

    begreen
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    It is fire code that black single wall pipe is only approved for connecting the stove to the chimney or for low heat applications. At a minimum the extension should be made out of stainless, but it will have all the caveats mentioned. WY climate may be dry, but it is cold and flue gases will condense immediately on the cold surfaces of the uninsulated pipe. It's a recipe for creosote production and a setup for a chimney fire.
     
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