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Sealing Stove Pipe?

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by boatboy63, Jan 21, 2011.

  1. boatboy63

    boatboy63 Member

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    Just wondering how many of you use a sealer on you stove pipe inside house. I have the black standard stove pipe running to a triple wall "thru the ceiling" When we first put it together the other day, it appeared to have gaps where they joined together. I did put 3 screws in the connections, 120* apart. Ended up using a stove cement on the joints, but it is too hard and seems you can hear it pop when it heats/cools. I would like to find something that can handle the heat and still flex. I know I have a very small leak at the junction between the pipe and the adapter that pushes into the box in the ceiling. Some of the cement that was put on the joints the other day, seem to have minor cracks in it.

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  2. webby3650

    webby3650 Minister of Fire

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    There is really no need to seal the joints, if they leak smoke you have a draft problem. A properly drafting flue pulls air in and will not smoke out.
  3. cmonSTART

    cmonSTART Minister of Fire

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    If you want to seal, stove cement is really your best option. High temp silicone will break down and evaporate at typical stove pipe temperatures. I've found that stove and gasket cement holds up pretty well, even with the pipe expansion.

    But like webby said, air shouldn't leak out of your pipe unless you have a draft problem.
  4. boatboy63

    boatboy63 Member

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    I understand what you guys are saying, but I am looking at it differently. There is no smoke coming back into the room...only lost room air going up thru the pipe. Since I did buy an EPA stove (Magnolia), I am just wanting to make sure I am "feeding" it properly. I was thinking of it like this, the more draft available, the better the performance on the stove. As the draft would actually be a vacuum, any sort of leak would feed the room air instead of pulling air thru the stove. Since an EPA stove requires a strong draft to work properly, any leak of it's vacuum would cause less performance.
  5. cmonSTART

    cmonSTART Minister of Fire

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    I like the way you think. Cram those gaps full of stove cement and you'll be OK. If someone knows of something better, please let us know.
  6. firefighterjake

    firefighterjake Minister of Fire

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    Thought about sealing up the stove pipe with stove cement . . . didn't get around to it in the first year . . . stove worked well so I never did get around to sealing up the pipe.
  7. Jonsered

    Jonsered New Member

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    Exactly the reason I am looking to seal my stope pipe too.
  8. Wood Heat Stoves

    Wood Heat Stoves Minister of Fire

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  9. Todd

    Todd Minister of Fire

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    Another good thing about sealing up the stove pipe is those little seams suck in relatively cooler air which creates creosote. Before I cemented my pipes together you could see the streaks of black where ever there was a gap when I took them apart for cleaning.
  10. boatboy63

    boatboy63 Member

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    Lowes sells some caulking in their paint department that is fire rated. It runs around $15 a tube. I am going to look closer at it next time I am in the store. Also, used the infrared thermometer and checked pipe temps. My black pipe is about 5' from top of stove to ceiling. I saw about a 100* drop in temps from within 6" of stove to ceiling. Is this normal or am I getting leakage from pipe where seam runs up and down?
  11. webby3650

    webby3650 Minister of Fire

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    Sealing the pipe joints isn't going to hurt anything, we only use Elmers and I see no room for cement in the joints. Woodstoves put out tons of heat, try not to think it to death. ;-)
  12. balsabones

    balsabones Member

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    I bought some extra fiberglass rope that is used to seal the glass, unraveled it into 1/16 strands and spot stuck it to my male end of black stove pipe. I let the silicone dry and then slid it all together. The small pieces of rope sealed the pipe. I did, "bunch" an little up at the place where you assemble the pipe, the vertical joint, so it would fill the gap. The further the pipe slid into each other, the tighter it got. No problems now.
  13. woodsmaster

    woodsmaster Minister of Fire

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    I recently installed a gassifacation boiler and didn't seal the pipe. big mistake on a induced draft appliance, I had smoke coming from every joint. Had to take apart and seal. Used some stuff for stoves that came in a caulk tube from rutland I think.
    Have a old natural draft stove in the house with no sealent and have never had a problem.
  14. Trktrd

    Trktrd Feeling the Heat

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    I also use stove cement on the inside pipe joints, mainly because I only have a 12' chimney and need all the draft I can get. Don't need leaky joints robbing my stove draft. Kind of a pain when pulling the pipe to clean, but it's a small sacrifice for a better burn.
  15. Dave_1

    Dave_1 New Member

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    http://www.marinepartssource.com/newdetails.asp?pnumber=BA70STBC650&mfg=BUCK ALGONQUIN&mfgno=70STBC650&desc=6 9/32 to 6 19/32 in. T-Bolt Band Clamp

    But it is like Webby stated:

    "There is really no need to seal the joints, if they leak smoke you have a draft problem. A properly drafting flue pulls air in and will not smoke out. "
  16. rustynut

    rustynut Feeling the Heat

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    bb63,
    Seems that you are quite worried about a very minor loss of room air............
    Have you thought about an outside air kit ?
    Seems to me that burning room air for the stoves combustion would be a much more substantial loss of room air ?
    I have found this to give me a much more balanced system as well as eliminating the room air burning that
    is concerning you.
    Something to think about..........
    rn
  17. VCBurner

    VCBurner Minister of Fire

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    If you use stove cemment you'll need to allow for proper curing. The stuff I use is supposed to sit for at least 2 hours I think before you attempt to do some break in fires. If you're sealing some bigger gaps like more than 1/8 " gap you'll need to allow longer curing time before breaking in the seals. Wipe the pipe with a damp rag before applying the cemment and allow it to dry.

    I have done it before and want to do it again when I finally get a liner for my chymney.
  18. woodsmaster

    woodsmaster Minister of Fire

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    Thats true for a natural draft appliance but not true on induced draft appliance.
  19. jimbom

    jimbom Combustion Analyzer

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    I go vertical from the stove to a metalbestos flue. I went to a pipeline supply yard and bought a 10 foot piece of steel pipe with a 0.20 inch thick wall. This pipe extends up into the flue about three foot and fits tightly into the stove collar. I was looking for something more substantial than the typical sheet metal stove pipe. Also, having lived in earthquake zones, experiencing earthquakes, and now being at the edge of the New Madrid zone, I try to make things resistant to horizontal ground motion. Especially things that may start fires. It is a heavy load for the stove to bear, but I have a steel stove that seems to hold up well. Not sure if a nice cast iron stove would work with this arrangement. It is painted black and looks good.
  20. Dave_1

    Dave_1 New Member

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    Please explain further because;

    after 30+ years our white ceiling looks as it did the first year. Initially I too used furnace cement to plug the gaps but the stuff would crumble. So after a few years of stuffing & no carbon monoxide alarm learned my worry was unfounded & give up on the furnace cement.

    However, if woodmaster wants to seal his connections that 6" T ring will do the job & give him peace of mind since that seems to be what he desires.
  21. woodsmaster

    woodsmaster Minister of Fire

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    My boiler as most gasifacation boilers has 2 fans that push air up the chimney and creates pressure. Any unsealed joint will leak. Like I said it is not necessary in a natural draft stove.
  22. Dave_1

    Dave_1 New Member

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    Ok, since boatboy was referring to his wood stove, & Webby & I addressed his issue, I fail to understand your post to me regarding my comment to his issue???
  23. woodsmaster

    woodsmaster Minister of Fire

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    I was just making conversation. You asked for further explanation so I give one.
  24. boatboy63

    boatboy63 Member

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    rusty,
    No worry about losing room air. My house isn't that tight. What I was concerned with was losing draft from roof to the stove by what was leaking thru the pipe at either the seams or joints. Picture it this way...take a standard drinking straw, put a very small pinhole in it 2" from the bottom. Stick the bottom of the straw 1" into a glass of water (leaving pinhole 1" above water line) and suck on the other end. You will see that it takes a significantly larger amount of suction or "draft" on the top of the straw to pull the water up. I know we aren't pulling liquid thru the stove, but whenever there is a vacuum involved and a small leak in it somewhere, it will substancially reduce the vacuum "draft" being pulled thru the stove. With room temperature air being sucked into pipe from leaks, it is cooling the pipe and promoting the accumulation of creosote. Look how a minor vacuum leak on today's cars will cause a check engine light.

    I got a larger stove mat and installed it yesterday. In order to do this, stovepipe had to be pulled down and stove moved to get old mat out and new one in place. At the same time, we took the pipe outside and used a wire brush on the bench grinder to remove the old cracked Rutland stove cement that I had used at first to seal it. This stuff was better than nothing, but it is a mortar that does not flex when dry. With constant expansion and contraction from heating and cooling down of the pipe, the cement will crack. I looked at the Rutland high-temp silicone, but it is only rated for 450* continuous and 500* intermittant. I ended up getting a tube of Permatex Ultra Copper high-temp silicone from an auto supply ($6.99). It is rated at around 625* continuous and 700* intermittant. After cleaning the old cement, we painted the pipe with stove paint, reassembled the pipe assembly to the stove, and installed 3 small screws to each joint. We placed a small bead of silicone around all joints and seams (including the 24" seam of each section of pipe) and used a finger to smooth it into the seams. We allowed it to dry several hours and started a small kindling fire (125-150* at the pipe) to just help speed up the curing process.

    Before going to bed, we built a small fire and let it go overnight. Checked this morning and all is good. Sealer is cured and no visible signs of cracking. In some areas of where the pipes join together, there was nearly a 1/4" gap and the silicone filled it nicely. Outside temps have warmed up for a few days but are forcasted to get cold again by the end of the week. I should be able to tell a difference by then. I will be able to get stove temps back up and will check my pipe temps at top of stove and at bonnet going into ceiling. I was getting around a 75-100* temperature drop in that 5' long area before with my infrared thermometer. We will see if this has made a difference.

    As for using clamps, it may work, but not sure considering 1 end of each pipe is tapered with a crimped edge. Still have the 24" seam running up each section of pipe to deal with. Also, I understand the problem with a forced draft boiler leaking smoke. My stove doesn't leak smoke, but instead, felt like it was sucking air into the pipes at the seams.
  25. PARKBOY

    PARKBOY New Member

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    How about taking a hand full of powder and blowing it lightly by the gaps and watch and see if it is sucked into the gaps?

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