Chimney Connection/Modified Wall Thimble

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PolrBear

New Member
Jan 19, 2019
35
Southwest Missouri
I bought a stove from another individual, complete with double-wall chimney pipe and a thimble kit to go through the wall. (DuraPlus by DuraVent, 10" OD/6" ID.) After the handyman and I finished installing the flue, we figured out that the wall thimble has been modified. This is what it looks like currently in my wall, the same way the original owner had it installed. Note the double wall pipe sticking all the way through, with the male end of the black pipe stuck into it:

upload_2019-1-19_20-55-54.png

The original wall thimble from Duravent looks like this, with a 6" hole in the middle rather than the enlarged hole you see above:

416V44gEQTL._SX425_.jpg

Having talked to Duravent tech support, it seems that the double wall pipe is supposed to be covered by the wall thimble, leaving only the 6" inner piece exposed for stove connection. Plus, you're supposed to have a "snap lock adapter" to connect to regular black pipe:

415UL54aQGL._SX425_.jpg

Getting the double wall pipe to terminate right where it needs to meet up with the wall thimble could be a real problem, if you need a certain amount of pipe to protrude from the outside wall in order to start your vertical run in the correct location. This was obviously the case with the previous owner, who found the easy redneck solution: Enlarge the wall thimble and stick the double wall pipe all the way through it.

This leaves me with a flue installation that 1) looks really dorky, and 2) doesn't meet the manufacturer's recommendation (though my insurance has approved it based on pictures). I'm considering the following possible solutions:
  1. Have a custom cap fabricated to go around the end of the double wall and allow the black pipe to pass through. With everything painted black, this would look fine, and would be pretty much just for cosmetic purposes.
  2. Purchase a new wall thimble and the snap lock adapter to go with it. I don't have the option of pushing the pipe further out through the wall, so I'd have to build a wood frame to bring out the black side of the thimble instead.
A stove guy told me I really need to go with Option 2 because (if I understood him correctly), you never want to install stove pipe male end up because anything that drips back down the chimney could get caught on the connection "lip" and either get stuck or find a way to leak out. My handyman scratched his head when I told him this, and said he always installs the pipe male end up. Can anybody enlighten me further on this?

Stove guy also cautioned that if the flue isn't installed in the manufacturer-recommended way, with the manufacturer-recommended parts, we could end up in trouble with our insurance in the event of a fire.

Input is appreciated.
 

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begreen

Mooderator
Staff member
Nov 18, 2005
90,660
South Puget Sound, WA
First thing, yes, the stove pipe is installed backward. The crimped end on the stove pipe should be toward the stove. This is so that any creosote will drip back into the stove and not down the sides of the pipe.

Second, that is a most un-kosher support system for the chimney pipe and it does not appear high enough to meet the 10-3-2 rule.

The horizontal run from the tee appears to be 6" too long. Where is the inside trim piece for the thimble? Did the end get cut off? The female end of the chimney section is supposed to mate tight with the black inner piece which gets nailed to the studs in the wall. At that point i thought the stove pipe just get crimped (so that both ends are crimped) and pushed into the thimble.
 
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HomeinPA

Minister of Fire
Jan 4, 2018
510
Central PA
I bought a stove from another individual, complete with double-wall chimney pipe and a thimble kit to go through the wall. (DuraPlus by DuraVent, 10" OD/6" ID.) After the handyman and I finished installing the flue, we figured out that the wall thimble has been modified. This is what it looks like currently in my wall, the same way the original owner had it installed. Note the double wall pipe sticking all the way through, with the male end of the black pipe stuck into it:

View attachment 238665

The original wall thimble from Duravent looks like this, with a 6" hole in the middle rather than the enlarged hole you see above:

View attachment 238667

Having talked to Duravent tech support, it seems that the double wall pipe is supposed to be covered by the wall thimble, leaving only the 6" inner piece exposed for stove connection. Plus, you're supposed to have a "snap lock adapter" to connect to regular black pipe:

View attachment 238668

Getting the double wall pipe to terminate right where it needs to meet up with the wall thimble could be a real problem, if you need a certain amount of pipe to protrude from the outside wall in order to start your vertical run in the correct location. This was obviously the case with the previous owner, who found the easy redneck solution: Enlarge the wall thimble and stick the double wall pipe all the way through it.

This leaves me with a flue installation that 1) looks really dorky, and 2) doesn't meet the manufacturer's recommendation (though my insurance has approved it based on pictures). I'm considering the following possible solutions:
  1. Have a custom cap fabricated to go around the end of the double wall and allow the black pipe to pass through. With everything painted black, this would look fine, and would be pretty much just for cosmetic purposes.
  2. Purchase a new wall thimble and the snap lock adapter to go with it. I don't have the option of pushing the pipe further out through the wall, so I'd have to build a wood frame to bring out the black side of the thimble instead.
A stove guy told me I really need to go with Option 2 because (if I understood him correctly), you never want to install stove pipe male end up because anything that drips back down the chimney could get caught on the connection "lip" and either get stuck or find a way to leak out. My handyman scratched his head when I told him this, and said he always installs the pipe male end up. Can anybody enlighten me further on this?

Stove guy also cautioned that if the flue isn't installed in the manufacturer-recommended way, with the manufacturer-recommended parts, we could end up in trouble with our insurance in the event of a fire.

Input is appreciated.
I agree with begreen and the stove guy. I would suggest getting online and finding the official manufacturer's installation instructions and just about start over. Remove the horizontal piece going into the house and move it to the top of the chimney as your current install is to short. Then measure and order the correct length of pipe (they probably have an adjustable length pipe available) along with the correct pass-through components and finish it correctly. Class-a chimneys are proprietary and you should not be making your own parts for them. It will void the chimney's UL listing and could cause other issues. (Regardless of what your insurance people tell you) I'd also look in to getting the proper T bracket for the bottom of the chimney for the same reason.
 

PolrBear

New Member
Jan 19, 2019
35
Southwest Missouri
First thing, yes, the stove pipe is installed backward. The crimped end on the stove pipe should be toward the stove. This is so that any creosote will drip back into the stove and not down the sides of the pipe.

Makes sense.

Second, that is a most un-kosher support system for the chimney pipe and it does not appear high enough to meet the 10-3-2 rule.

Yes, it looks like it misses 3' by a few inches to a foot on the uphill side of the pipe. I've burned several fires and the flue seems to draw fine. Do you think evil consequences might follow if we don't extend the chimney?

The horizontal run from the tee appears to be 6" too long.

4.5" to be exact.

Where is the inside trim piece for the thimble? Did the end get cut off?

The thimble is complete, as far as I can tell, except that the inside trim piece was reamed out (by the previous owner) to allow the pipe to pass through.

The female end of the chimney section is supposed to mate tight with the black inner piece which gets nailed to the studs in the wall. At that point i thought the stove pipe just get crimped (so that both ends are crimped) and pushed into the thimble.

According to DuraVent, I need a snap lock adapter as well, unless I'm using their DuraBlack pipe (and I'm not). If I'm going this far to ensure my chimney is compliant, I'll probably pony up the money to go all the way.

I agree with begreen and the stove guy. I would suggest getting online and finding the official manufacturer's installation instructions and just about start over.

What I've found is in the form of the DuraPlus catalog, which has helped clarify things to this point.

Remove the horizontal piece going into the house and move it to the top of the chimney as your current install is to short.

I actually have an extra 3' section we didn't use that we can go ahead and install if necessary. I'm somewhat concerned that it's going to make the chimney unstable, though, due to the extra weight and height.

Then measure and order the correct length of pipe (they probably have an adjustable length pipe available) along with the correct pass-through components and finish it correctly.

Alas, according to my stove guy they make no adjustable piece. DuraPlus comes in 1' increments, meaning this piece (4.5" too long) is the closest I'll get without moving the whole chimney.

The DuraPlus wall thimble states in the manufacturer directions that you can adapt it to fit a wall up to 16" thick. So, my plan is to beef out just that part of the wall with a wood frame, thickening it to where the stove pipe terminates to a sturdy thimble mount at the right spot. Painted, it shouldn't look too ugly. Any reason this won't work?

Class-a chimneys are proprietary and you should not be making your own parts for them. It will void the chimney's UL listing and could cause other issues. (Regardless of what your insurance people tell you) I'd also look in to getting the proper T bracket for the bottom of the chimney for the same reason.

I have the manufacturer T bracket. Problem is it's only meant to wall mount, and my chimney is too far from the wall. That's why we had a support custom-fabricated from steel. It's screwed to the concrete block below and in my opinion represents a significant improvement on the strength of the DuraVent-supplied T bracket.
 

HomeinPA

Minister of Fire
Jan 4, 2018
510
Central PA
I actually have an extra 3' section we didn't use that we can go ahead and install if necessary. I'm somewhat concerned that it's going to make the chimney unstable, though, due to the extra weight and height.

There should be a roof support brace that would run down to the roof and brace the part above the overhang. Page 14 of the parts list.


Alas, according to my stove guy they make no adjustable piece. DuraPlus comes in 1' increments, meaning this piece (4.5" too long) is the closest I'll get without moving the whole chimney.

The DuraPlus wall thimble states in the manufacturer directions that you can adapt it to fit a wall up to 16" thick. So, my plan is to beef out just that part of the wall with a wood frame, thickening it to where the stove pipe terminates to a sturdy thimble mount at the right spot. Painted, it shouldn't look too ugly. Any reason this won't work?

Remember to keep a 2" clearance to the framing...including the drywall
 

PolrBear

New Member
Jan 19, 2019
35
Southwest Missouri
There should be a roof support brace that would run down to the roof and brace the part above the overhang. Page 14 of the parts list.


Remember to keep a 2" clearance to the framing...including the drywall

Thanks for those tips. I've pretty much decided we need to raise the height of the chimney, though it will be a pain to reconstruct our scaffolding and go back up there. I've also ordered the parts to build out the wall thimble as outlined above.
 

webby3650

Master of Fire
Sep 2, 2008
11,062
Indiana
Thanks for those tips. I've pretty much decided we need to raise the height of the chimney, though it will be a pain to reconstruct our scaffolding and go back up there. I've also ordered the parts to build out the wall thimble as outlined above.
Scaffolding? That’s an easy roof, can’t see needing scaffold to add a piece to the top.
How close is the pipe to ceiling? That thimble looks really high to me for single wall pipe.
 

PolrBear

New Member
Jan 19, 2019
35
Southwest Missouri
Scaffolding? That’s an easy roof, can’t see needing scaffold to add a piece to the top.
How close is the pipe to ceiling? That thimble looks really high to me for single wall pipe.

Adding the top piece is a little complicated by the fact that we can't get the cap off. What we'll have to do is remove the top piece (which involves undoing the support bracket) and insert the final 3' section where that is. I guess it could be done with just a tall ladder, but scaffolding is how my handyman had it put together to work when we did it before, with me on a ladder on the scaffolding and him on the roof.

We have the requisite 18"+ clearance from the single-wall pipe to the ceiling.
 

webby3650

Master of Fire
Sep 2, 2008
11,062
Indiana
What stove is hooked to it?
 

PolrBear

New Member
Jan 19, 2019
35
Southwest Missouri
Yeah, $450 for the stove plus all the double wall pipe. Paid the handyman $570 so far for installation labor and the parts he's provided. Expect to pay another $150 for the parts that have been mentioned here, plus whatever he charges to make the modifications I need, so looks like $1500 should cover it all at the end of the day.
 

webby3650

Master of Fire
Sep 2, 2008
11,062
Indiana
Yeah, $450 for the stove plus all the double wall pipe. Paid the handyman $570 so far for installation labor and the parts he's provided. Expect to pay another $150 for the parts that have been mentioned here, plus whatever he charges to make the modifications I need, so looks like $1500 should cover it all at the end of the day.
Not bad! That’ll be a good stove for you. Contacting dura-vent was the correct thing to do, seems like you are on the right track now.
 

PolrBear

New Member
Jan 19, 2019
35
Southwest Missouri
So I realize this setup still isn't the height of orthodoxy, but we're now using the "correct" parts for the double-to-single wall hookup, and I feel pretty comfortable with the result. Thanks for the help, everyone!

upload_2019-2-2_9-17-53.png upload_2019-2-2_9-18-2.png upload_2019-2-2_9-18-11.png
 
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begreen

Mooderator
Staff member
Nov 18, 2005
90,660
South Puget Sound, WA
That's a good improvement.
 

webby3650

Master of Fire
Sep 2, 2008
11,062
Indiana
So now all that’s left is a proper Tee support, add to the chimney height, and switch the stove pipe out for 22 gauge? ;)
In all seriousness, I’m glad you’ve got it on the run now.
 

PolrBear

New Member
Jan 19, 2019
35
Southwest Missouri
Looks good from where I'm sitting. How is it working?

Ironically, the weather has stayed warm since we finished the improvements. Thinking we'll have occasion to put our setup through its paces later this week!

So now all that’s left is a proper Tee support, add to the chimney height, and switch the stove pipe out for 22 gauge? ;)
In all seriousness, I’m glad you’ve got it on the run now.

Well, you can look sideways at my chimney tee support if you want, but I'm quite proud of it! :cool: Much sturdier, in my opinion, than the thin sheet metal bracket the manufacturer supplies.

As to the chimney height, my handyman measured it to be 32" above the peak of the roof, so if I understand the 10-3-2 rule correctly, we're golden. :)

What would be the advantage of 22ga stove pipe?
 

begreen

Mooderator
Staff member
Nov 18, 2005
90,660
South Puget Sound, WA
Well, you can look sideways at my chimney tee support if you want, but I'm quite proud of it! :cool: Much sturdier, in my opinion, than the thin sheet metal bracket the manufacturer supplies.
I haven't seen a factory chimney bracket that's properly installed fail yet. Does this pole supported system still allow good access to clean-out cap on the bottom of the tee?
 

webby3650

Master of Fire
Sep 2, 2008
11,062
Indiana
Ironically, the weather has stayed warm since we finished the improvements. Thinking we'll have occasion to put our setup through its paces later this week!



Well, you can look sideways at my chimney tee support if you want, but I'm quite proud of it! :cool: Much sturdier, in my opinion, than the thin sheet metal bracket the manufacturer supplies.

As to the chimney height, my handyman measured it to be 32" above the peak of the roof, so if I understand the 10-3-2 rule correctly, we're golden. :)

What would be the advantage of 22ga stove pipe?
Is the tee support sitting on the ground?
22 ga pipe is much sturdier, the elbows aren’t adjustable, and the good stuff has welded seams. It’s not a necessity, but it’s a nice upgrade.
 

PolrBear

New Member
Jan 19, 2019
35
Southwest Missouri
I haven't seen a factory chimney bracket that's properly installed fail yet. Does this pole supported system still allow good access to clean-out cap on the bottom of the tee?

Yes, the guy who fabricated the support patterned it after the factory bracket shape. There's a metal plate that slides out to allow access up into the tee, just as with the original. One issue with the factory bracket is that they only seem to make one to go right up against the wall, where this one needs to be a couple feet out to circumvent the eaves.

Is the tee support sitting on the ground?

The tee support is screwed to a concrete block which is set into the ground. I have a couple of metal shims that can be added, should the soil settle enough to affect the tee support.
 

begreen

Mooderator
Staff member
Nov 18, 2005
90,660
South Puget Sound, WA
Sounds good. My main concern is the long horizontal run going out to a cold chimney. That will slow down flue gases quite a bit. Keep an eye on build up there. FWIW I think I would have either cut the eave or done an offset.
 
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