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Small Cabin Forum / Cabin Construction / 6" stove to 8"pipe?
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lburners
Member
# Posted: 6 Mar 2021 18:01 - Edited by: lburners
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Did a little web search with mixed opinions. I can get some free 8" insulated pipe and I have a stove with a 6" flue. Would be very pleased to not buy a bunch of 6" insulated pipe. Thinking I would go 8ft or so uninsulated 6" pip adapted to the 8" insulated which go another 8'.

Irrigation Guy
Member
# Posted: 6 Mar 2021 18:27 - Edited by: Irrigation Guy
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Not sure if a larger size would effect your draft but you could probably sleeve 6” stove pipe right through it if it was ever an issue for minimal expense. Pose the question over on hearth.com

ICC
Member
# Posted: 6 Mar 2021 19:45 - Edited by: ICC
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An increase in flue size like that almost always is not good. A six-inch pipe has a cross-section area of 28 sq. in. An 8-inch pipe has a cross-section area of 50 sq. in. That large increase means the gases will slow down a huge amount when it hits the 8 inch section. Possibly not good for the draft.

lburners
Member
# Posted: 6 Mar 2021 20:37
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Yeah I was concerned that might be the case. Thanks for the input. If anyone on here has done it with success let me know. Otherwise I will keep looking for some matching 6" pipe.

ICC
Member
# Posted: 6 Mar 2021 20:38
Reply 


The reason many newer stoves use a six inch flue is the increased efficiency. They actually flow air through the burn chamber more slowly than older stoves. They burn more completely once warmed up. The manufacturers found that decreasing the flue size helped keep the chimney gases flowing better, maintaining a better chimney draft. Using an 8-inch flue counteracts that.

There are 6 inch liners made for use inside a masonry chimney. I'm not sure how one would go about using one inside a metal chimney. It seems like achieving s safe seal between the inner liner and the larger pipe might be a problem point.

gcrank1
Member
# Posted: 6 Mar 2021 22:12
Reply 


Wait for the right stuff. It is going to take just as much work to do it wrong as do it right and you might end up doing it twice.....

Brettny
Member
# Posted: 7 Mar 2021 05:53
Reply 


How many feet of insulated pipe do you need? The 6in stuff isnt like the price of gold.

I'm also not sure I would put used stuff in if you have insurance. They prob wont like old insulated pipe. Any of the used stuff I see is a beat to hell and they want big money for it.

Bruces
Member
# Posted: 7 Mar 2021 08:25
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Pick up the free pipe ,and trade it for the pipe you need .

Fanman
Member
# Posted: 7 Mar 2021 08:55 - Edited by: Fanman
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FWIW, our coal stove has a 5" outlet. 5" black stovepipe is still available, but it goes into a 6" insulated pipe to go through the roof and it works fine. Though it also worked in the old cabin when it went into a 4" pipe that ran about 3 feet horizontally through the wall...

A topic of interest to me, though. Our current wood stove is 8" and so is the chimney, but I'd like to replace it (the stove, not the chimney) and all the new ones are 6".

Nobadays
Member
# Posted: 7 Mar 2021 09:09
Reply 


I think you have your answer but we did have this scenario, to a point. The PO had, right at the stove used an increaser to go from 6" to 8" uninsulated pipe which then extended about 18'up near the peak where the triple wall goes through the roof. Always had draft problems. We replaced all the uninsulated 8" with 6" (hopefully this year replace the upper 8'-10' of that with double wall). We left the 8" that goes through the roof as it is only about 4' of pipe.

The draft improved noticeably! AND the horrible creosote build up issues we had were eliminated. The increase to 8" at the roof hasn't affected performance and doesn't collect a lot of creosote either. The 18' of single wall IS TOO much and though we did not creosote up badly this winter, that may have been in part because we replaced our stove with a BK catalytic wood burner.

lburners
Member
# Posted: 7 Mar 2021 16:40 - Edited by: lburners
Reply 


Well I grabbed for at the very least to make a couple bucks. This might be my chance to post in that deals thread.
image20210307_161642.jpg
image20210307_161642.jpg


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