Flue size 6" vs 8"

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new_wood

new_wood

Member
May 9, 2011
73
Lebanon, Ohio
We are researching freestanding wood burning stoves for our new addition. A friend told me to make sure I get a stove with an 8" flue.....he said that the creosote doesn't "plug" the pipe as quickly instead of a 6" flue..............any truth to this? Most of the stoves I have been researching so far have been 6" flue size. My thoughts are that if I burn good dry wood and regularly clean then the creosote build up isn't a concern. Thanks in advance for your input.
 
You are correct. Your friend must be huffing flue gas.
 
Denny said:
We are researching freestanding wood burning stoves for our new addition. A friend told me to make sure I get a stove with an 8" flue.....he said that the creosote doesn't "plug" the pipe as quickly instead of a 6" flue..............any truth to this? Most of the stoves I have been researching so far have been 6" flue size. My thoughts are that if I burn good dry wood and regularly clean then the creosote build up isn't a concern. Thanks in advance for your input.
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You are right, your friend is wrong . . . end of story.

Welcome to the forum . . . and the fount of all knowledge . . . well at least any knowledge that has to deal with wood burning.
 
If your friend is plugging up a 6" pipe with creosote then he has a serious problem. I dont' get more than a handful of dry powder out of my chimney after a full year of burning. Just burn dry wood and you won't have a problem.

Edit: Do not put the chimney in until you have decided what stove you want to use as an 8" flue for a stove that requires a 6" flue will make the stove not perform well
 
Even burning marginally seasoned wood I only had a light powder of build up in the top 3-4 ft of pipe. I guess technically speaking a pipe of a smaller diameter would get plugged up sooner than a larger pipe. Does your friend know that the great majority of stoves come with 6 inch exhaust? All but the largest stoves have 6.... :-/
 
If you have so much creosote in the chimney that it actually reduces draft and "plugs" the chimney, god help you if you ever had a chimney fire as that would be a TON of fuel in either a 6 or 8 in pipe.

You came to the right place, welcome!

pen
 
The friend is blowing smoke. Dry wood + warm flue + good burning habits will keep a 5" flue clean.
 
Hey, that is good advice. I am going to try to find 12 inch flue pipe so I can just cut live trees and burn 'em the same day I cut 'em for years on end without the hassle and expense of chimney cleaning. At first my stove might not work exactly right, but after a couple of years I'll be down to a 6 inch pipe again and I should be good to go.
 
on a completely unrelated to burning thought....6" is safer, because it is much harder for the average person to get their head stuck in it....8" is just the right size for someone to try...then its like those chinese finger cuffs. 6" class A pipe is also a bit less expensive than 8" so you could "win" on many fronts.
 
I should have added to my previous comment that even burning dry, seasoned wood . . . you still want to inspect and clean out the chimney on a regular basis since some creosote can form over time . . . albeit much more slowly if you burn seasoned wood, run the stove properly and burn at the proper temps.
 
Denny, to let you know what can happen when you burn good wood, we put up a new SS chimney at the same time we installed the Fireview. That was 4 years ago. So far we've gotten around a cup of soot and no creosote. We've cleaned our chimney one time in that 4 year span. Well, my wife did sort of bang on the inside of the pipe one day because she could see something up there but hardly anything came out.


In addition, it is best to have the proper size chimney. If your stove calls for a 6" then it is best to have a 6" chimney. If it has an 8" then put in an 8".
 
Funny this just came up. I had a guy come out today to look at my chimney which needs a major rebuild and he also does the Supaflue system. He told me he would rather have a 7" supaflue than a 6" because the 6" clogs up faster and you won't have to worry about cleaning as often. I said why not just burn dry wood, he says, I have a chimney fire once or twice per year and just let her rip, cleans it up just fine. :bug: I guess that old woodburners trick is still alive and kickin.
 
No Todd. That is not an old woodburner's trick. It is an old fool's trick. Shows lack of intelligence for sure.
 
Actually, you are more likely to plug up a flue connecting a 6" flue stove to an 8" pipe than connecting it to a 6" pipe. Going to a larger pipe size than the stove has slows down the flow of smoke. This is especially true when there are factors affecting draft like a a short chimney, cold outside chimney or multiple elbows in the smoke path.

In other words, if you have a 8", 30 ft tall indoor chimney you may not have any issues. But if you have a 12' outside 8" chimney connected to the stove via an outside tee and an inside elbow, you stand a good chance of having lousy draft and creosote buildup.
 
I bought my first stove in 2004,a quad 5700 with a six inch flue.I got rid of it in Jan. 2011,and put in an 8 inch the 6 inch stailess steel liner in a masonry chimney had never been cleaned ,only visibly inspected. When it was removed I had less than 2 cups of buildup. Listen to these men they speak the truth. Proper draft,dry wood= clean flues.
 
Todd said:
Funny this just came up. I had a guy come out today to look at my chimney which needs a major rebuild and he also does the Supaflue system. He told me he would rather have a 7" supaflue than a 6" because the 6" clogs up faster and you won't have to worry about cleaning as often. I said why not just burn dry wood, he says, I have a chimney fire once or twice per year and just let her rip, cleans it up just fine. :bug: I guess that old woodburners trick is still alive and kickin.
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I think I would look for someone else to do my chimney. . . .
 
Delta-T said:
on a completely unrelated to burning thought....6" is safer, because it is much harder for the average person to get their head stuck in it....8" is just the right size for someone to try...then its like those chinese finger cuffs. 6" class A pipe is also a bit less expensive than 8" so you could "win" on many fronts.
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Interesting point, thanks for the "heads up".
 
When you select a stove appropriate for your installation, you'll find that the manufacturer's instructions will include specific information regarding the flue size. There are still some stoves out there with 8" flue collars, but the vast majority are 6". I've never yet heard of a manufacturer who didn't recommend (require) that the entire flue from stove to daylight be the same diameter as the flue collar. Lots of folks have made it (changing diameters) work in retrofit situations, but if you're doing a whole new install, do it by the book. 8" flue collar = 8" flue, 6" flue collar = 6" flue. And "the book" comes from the folks who built the stove and paid to have it tested and certified...not from your uninformed buddy. Rick
 
Todd said:
Funny this just came up. I had a guy come out today to look at my chimney which needs a major rebuild and he also does the Supaflue system. He told me he would rather have a 7" supaflue than a 6" because the 6" clogs up faster and you won't have to worry about cleaning as often. I said why not just burn dry wood, he says, I have a chimney fire once or twice per year and just let her rip, cleans it up just fine. :bug: I guess that old woodburners trick is still alive and kickin.
Click to expand...

Not to take this thread off topic, but when I was looking for someone to reline my chimney, one of the guys I talked to wanted to put in a 7 inch liner. I can't remember the exact reasons, but it was pure BS - so needless to say, he didn't get the job.

If you are relining and have the space, I really like the Rhino rigid liner used in my chimney with the 1/2 inch wrap. I like the smooth surface and the heavy wall.

BTW, it ain't clogged-up so far ;)

Bill
 
Todd said:
Funny this just came up. I had a guy come out today to look at my chimney which needs a major rebuild and he also does the Supaflue system. He told me he would rather have a 7" supaflue than a 6" because the 6" clogs up faster and you won't have to worry about cleaning as often. I said why not just burn dry wood, he says, I have a chimney fire once or twice per year and just let her rip, cleans it up just fine. :bug: I guess that old woodburners trick is still alive and kickin.
Click to expand...

After reading your post I just had to look and see if you were from NH. I had a Supaflu installed a couple of months ago by a guy that has been in the business for a very long time. He also comes highly recommended by many.

I went back and fourth with him for some time. He insisted that I go with a 7" flu despite my telling him that Woodstock recommended that I go with a 6" flu for thier Progress Hybrid.

The owner said that a 7" flu would leave room for creosote build up if there is to be any. I should him the 16 cords of three year old dried maple and oak in my backyard and explained to him that I didn't think I would get any build up. He still insisted on the 7" flu.

My thought was that maybe the bigger the hole the less materials they use.... But I doubt this is the case.
 
dpgoalie said:
Todd said:
Funny this just came up. I had a guy come out today to look at my chimney which needs a major rebuild and he also does the Supaflu system. He told me he would rather have a 7" supaflue than a 6" because the 6" clogs up faster and you won't have to worry about cleaning as often. I said why not just burn dry wood, he says, I have a chimney fire once or twice per year and just let her rip, cleans it up just fine. :bug: I guess that old woodburners trick is still alive and kickin.
Click to expand...

After reading your post I just had to look and see if you were from NH. I had a Supaflu installed a couple of months ago by a guy that has been in the business for a very long time. He also comes highly recommended by many.

I went back and fourth with him for some time. He insisted that I go with a 7" flu despite my telling him that Woodstock recommended that I go with a 6" flu for thier Progress Hybrid.

The owner said that a 7" flu would leave room for creosote build up if there is to be any. I should him the 16 cords of three year old dried maple and oak in my backyard and explained to him that I didn't think I would get any build up. He still insisted on the 7" flu.

My thought was that maybe the bigger the hole the less materials they use.... But I doubt this is the case.
Click to expand...

Yeah, he was really pushing the 7" until I said maybe I'll just reline it myself and he backed right off and went with the 6". He was definitely concerned about the amount of supaflue mix he had to use and I had a pretty large hole to fill after he busted out the old clay tiles. I guess that mix isn't cheap.
 
The problem with an 8 or 7 inch chimney is that the appliance may struggle to heat-up the air volume contained inside the chimney. A hot chimney is required to create enough draft. Poor draft will inevitably lead to poor combustion, which will cause smoke roll backs, a dirty glass, lack of heat, and a large quantity of unburnt fuel inside the firebox.
 
I cam across a great deal on CL for some 8" class A. I put this in my parents house along with the country flame smoke dragon that came with it. My thoughts were this: Run that stove until something better comes along priced right, if it requires a 6" chimney then just drop a SS liner down the inside of the 8 and rock out. Anyone see any flaw with that logic? I understand when buying NEW that its smart to buy once, but hey cant pass up 21' of class A (and a stove) for $265!

Jason
 
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