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creosote-- what is it and where does it come from?

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by stovepipe?, Dec 20, 2005.

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  1. stovepipe?

    stovepipe? New Member

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    I’m new to the world of wood stoves, and am wondering how to keep my newly installed stove and chimney liner clean. So I have a few questions for the veterans about how creosote buildup happens

    I understand that running the stove hot will reduce creosote. Is that because the gasses that end up in the flue are cleaner, or because hot stove means hot flue with good draft, so less lingering, cooling gasses? what exactly is it and under what conditions does it form deposits.

    I usually keep my stove running around 500 degrees, almost completely dampered down (burning oak for the most part). I have a 30 foot interior chimney w/ an insulated flex liner in it. When the stove is at 500, the stove pipe a few feet up will be only at around 200. I assume it just gets cooler the higher up the flue one measures. But I have very strong draft (hence need to damper down). So what should I do to minimize creosote buildup, and how often should I clean (and how can I tell when it needs it—i.e. what counts as dirty? A thin film, ¼ inch chunks?)

    also, do these burn-one-a-month creosote reducing logs work? worth using or not?\

    thanks

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  2. Eric Johnson

    Eric Johnson Mod Emeritus

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    That's a whole bunch of questions. I'll try to answer the ones I feel qualified to comment on.

    The answer to your first question is: both. A hot stove (catalytic, secondary combustion, old tech) will produce less creosote in the pipe because a lot of it is burning up before it hits the chimney. The smoke that goes into a hot chimney is less likely to stick to the walls. Like my dad always said, "you want your creosote to wind up on your neighbor's car, not in your chimney." A stainless liner, especially an insulated one in an interior chimney, gets hot quick and stays that way.

    A strong draft is another factor that helps cut creosote formation, in part because it pulls the smoke out faster, and in part because it keeps the stove burning hotter.

    What's acceptable as far as creosote formation and what isn't? Tough question. Every installation is different. Ideally, you want zero creosote. And you could get that under the right circumstances. Some stoves, furnaces and boilers generate a lot, and some none at all. If you can look up or down your chimney and see chunks of creosote growing on the liner walls, then it should probably be cleaned. Usually in that case, there will be chunks of the stuff in the cleanout. That's another tip-off.

    If your chimney is easily accessible from below, then I would recommend getting yourself a poly brush (same diameter as the liner), and enough fiberglass rods to reach to the top of the chimney. Run it up there once a week for awhile (and under different burning conditions, i.e., warm weather, cold weather/heavy use, light use) until you get a feel for how much your stove is producing. Then put together a cleaning schedule that will keep it clean.

    In another house, I had a wood-fired boiler for 10 years and I got into the habit of cleaning the chimney once a week, whether it needed it or not. The whole process took about 15 minutes. I slept a lot easier at night. But I'm kind of obsessive on some things. A clean chimney is probably something worth obsessing about.
  3. Eric Johnson

    Eric Johnson Mod Emeritus

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    ^^^^^Doubtful.

    I wouldn't bet the house on it.

    I just wanted to add (and both Dylan and I can attest to this, I think) that when using a poly brush and fiberglass rods, be sure the stove is basically out and the chimney basically cool before you go sticking a rod and brush up there. It doesn't take much to melt either one.
  4. webbie

    webbie Seasoned Moderator Staff Member

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    You got it!

    Creosote, or tars (another name) form in the chimney for two reasons:
    1. These combustibles are not properly burned in the stove or fireplace fire.
    2. They are not exhausted quickly enough and condense on a relatively cool surface.

    So, take any combination of the above and creosote can happen. A great stove with a mediocre cool chimney might make no creosote at all, but a dirty stove with a great chimney might!

    So, in the inverse, to avoid creosote burn as efficiently as possible and have a warm chimney!
  5. stovepipe?

    stovepipe? New Member

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    thanks for the input. can you tell me a little more about the fiberglass rods? I could access from below, but through an ash cleanout door. Are the rods flexible enough to make the bend through the door, into the chimney? Also, any suggestions for where to buy them? (the cheaper the better, of course).

    thanks
  6. Roospike

    Roospike New Member

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    "Flex Rods" U can buy them at your local farm store , box store , hardware stores , Wal-Mart , K-Mart , Target , ect...ect....
  7. Eric Johnson

    Eric Johnson Mod Emeritus

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    As Roospike says, they're available all over the place. I know they have them at Home Depot and Lowe's. And they're not expensive, all things considered. I think a 4-foot rod goes for between $5 and $10. And yes, they're pretty flexible. If you have a cleanout that's at least 3 or 4 feet off the floor, you should have no trouble pushing the brush up into the chimney, screwing in sections as you go. Don't be afraid to push hard to get it "around the corner." The resistance you feel is just the brush adjusting itself into the liner.

    One thing I always do is keep a can of WD-40 (In Iraq they use WMD-40) handy to squirt and clean the rod threads before you screw them together. That will keep them from jamming up, which they do when they're dirty because the threads are aluminum and chimney soot is really fine. You might also want to keep a pair of pliers AND vice grips handy, just in case they still won't come apart when you're trying to wrap things up.
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