Advantages/Disadvantages of 6" and 8" Piping

[Easyellis8]

Just curious about the major differences between the use of either pipe size. Looking on the web it seems that the 8 inch pipe is more expensive; besides the cost are there advantages/disadvantages that one has over the other? Most stoves that I'm considering are 6 inch but one are two are 8 inch.

Just Curious!

 

[fossil]

The major advantage to either over the other is having an installation which follows the stove manufacturer's recommendation for an optimally efficient system. Generally, the entire flue assembly should have the same inside diameter as the flue collar on the appliance. Rick

 

[Easyellis8]

So, other than following the manufacturer's guidance one size doesn't draft better than the other? Can an 8' flue from the stove be decreased to a 6' up through the ceiling our out of the wall or can a 6' be increased in the same manner?

 

[fossil]

The size which is most likely to have the better draft is the size the manufacturer of the appliance recommends. Certainly there are installations that go both ways...some increasing and some decreasing. Sometimes they even work OK. But when it gets right down to it, I really think you're better off going with a flue system that's the same size as your flue collar. Rick

 

[begreen]

8" pipe can be decreased to 6" for the connector to the stove, but not vice versa. That's probably the best advantage for 8" if you were considering a universal flue installation. But if the stove is 6" and the flue height is just one story, then increasing to 8" may result in marginal draft. The majority of stoves these days are 6", so that's what we went with.

 

[karri0n]

I've recently discovered that my 6" stovepipe goes into an 8" liner above the blockoff plate, and I get massive draft with this configuration.

Am I in code violation, or am I outside of NFPA guidelines at all?

 

[fossil]

I've recently discovered that my 6" stovepipe goes into an 8" liner above the blockoff plate, and I get massive draft with this configuration.

Am I in code violation, or am I outside of NFPA guidelines at all?

It's not a code violation that I know of. NFPA 211 only addresses connection of a solid fuel-burning appliance into an existing masonry chimney, and says the existing chimney must be at least as large in cross-sectional area as the flue collar on the appliance, then goes on to say how much larger is acceptable. NFPA 211 is a "Standard", not a law or a code, unless adopted as such by the local Authority Having Jurisdiction. If your system works well, I wouldn't worry about it. Rick

 

[Easyellis8]

8" pipe can be decreased to 6" for the connector to the stove, but not vice versa. That's probably the best advantage for 8" if you were considering a universal flue installation. But if the stove is 6" and the flue height is just one story, then increasing to 8" may result in marginal draft. The majority of stoves these days are 6", so that's what we went with.

Thanks for the info, I'm getting my head around it now.

 

[Easyellis8]

The size which is most likely to have the better draft is the size the manufacturer of the appliance recommends. Certainly there are installations that go both ways...some increasing and some decreasing. Sometimes they even work OK. But when it gets right down to it, I really think you're better off going with a flue system that's the same size as your flue collar. Rick

Thanks for the explanation.

Ed

 

[begreen]

I've recently discovered that my 6" stovepipe goes into an 8" liner above the blockoff plate, and I get massive draft with this configuration.

Am I in code violation, or am I outside of NFPA guidelines at all?

That should be ok. If you were going from an 8" stove flue outlet to a 6" liner, that would be an issue, unless excepted by the stove manufacturer.

 

[mtnhome]

FWIW. I just got finished installing and hooking up my stove which has a 6" collar to an 8" chimney. I had originally picked up a VC stove and found a great deal(NOS) on 8"HT insulated pipe, Tee, and other parts. I then sold the VC and picked up a barely used Scan. My set up has about 4ft of 6" single wall to a 90 elbow connecting to a 6"-8" increaser connecting to the 8" Class A thru the thimble, into the tee and up about 23ft of enclosed chimney. I was a little worried about draft but from the 1st time I lit kindling in it, I have had great draft and no trouble controlling the burn. I think the thing that helps is the length of stack. In my case I got my 8" pipe for half of what 6" would have cost but ordinarily, 8" will cost much more than 6" and that needs to be considered. Only consider using 8" if you even imagine that you might in the future go from a 6" stove to an 8". Otherwise, save the bucks on chimney costs and put it into a nicer stove with a 6" flue.

 

[[email protected]]

i have and 8 reduced now into six, where should i put the reducer. pipe comes out back of stove, goes up to ceiling and bends into wall thimble and out side wall and up side of house, could be why i'm getting bad draft. where is the best place to reduce 8 into six. annie

 

[Wet1]

i have and 8 reduced now into six, where should i put the reducer. pipe comes out back of stove, goes up to ceiling and bends into wall thimble and out side wall and up side of house, could be why i'm getting bad draft. where is the best place to reduce 8 into six. annie

Did you read this thread before posting?

 

[rumme]

once again, we can see that different people have differnt opinions on these things.

example : the dealer I purchased my woodstove from told me that going from 8 " to 6 " { when the stove calls for 8 " } is not a good thing to do...

yet, he told also told me that going from 6 " - 8" usually isnt a big problem.

I went from 6 " round pipe to 8 " square chimney and my draft is GREAT....my chimney is only 16 ft tall and it is single walled uninsulated, and doesnt even get hot to the touch where the stovepipe connects to the chimney base.

this proves to me, that a good draft is not majorily dependant on a hot chimney or sticking to 6" piping when the woodstove has a 6" stovepipe outlet.

My 16 ft - 3/16 " thick steel chimney cost me about $200 and weighed about 400 lbs. Even though I do get alot of condensation, which drains out my bottom cleanout, im hoping this chimney will last at least 20 years.

my local steel supplier did have 6 " square chimney, but it was only 1/8" thick ..

 

[begreen]

Try that in Maine and you'd likely be sucking smoke down the flue. Even in Arkansas I suspect the condensation will pay it's toll in accumulated glaze in the upper parts of the flue.