How to make doublewall pipe watertight

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cptcrnch

New Member
Sep 10, 2025
2
Elizabeth IN
Hi guys! VERY newbie here, so I apologize for any confusion my post may have in it. I searched and didn't find this answer. I have a pole barn with a woodstove. Verticle 6" stove pipe going up, a 90 going out thru barn wall, double wall going thru barn wall; another 90 going up with a verticle pipe for chimney. To be clear, On the verticle barn wall I have my double wall pipe going thru barn wall to the outside and I have my stove pipe going attached to the doublewall providing my chimney. The double wall pipe sits horizontal (with a very slight tilt out wards/downwards so water runs away from wall); Very typical and simple design I thought! I cannot for the life of me get the double wall stove pipe to seal out water. Seems like the heat of double wall destroys anything I've put around it to seal it....and then I get water in it. Is there a product that makes the double wall watertight btwn the double wall and the barn wall. Is there a heat resistant caulk? gasket? what fits around the double wall to keep water out? any and ALL input is MUCH appreciated! Thank you in advance! - JR
 
Hi guys! VERY newbie here, so I apologize for any confusion my post may have in it. I searched and didn't find this answer. I have a pole barn with a woodstove. Verticle 6" stove pipe going up, a 90 going out thru barn wall, double wall going thru barn wall; another 90 going up with a verticle pipe for chimney. To be clear, On the verticle barn wall I have my double wall pipe going thru barn wall to the outside and I have my stove pipe going attached to the doublewall providing my chimney. The double wall pipe sits horizontal (with a very slight tilt out wards/downwards so water runs away from wall); Very typical and simple design I thought! I cannot for the life of me get the double wall stove pipe to seal out water. Seems like the heat of double wall destroys anything I've put around it to seal it....and then I get water in it. Is there a product that makes the double wall watertight btwn the double wall and the barn wall. Is there a heat resistant caulk? gasket? what fits around the double wall to keep water out? any and ALL input is MUCH appreciated! Thank you in advance! - JR
Red RTV and maybe a metal sub roof?
 
Stove pipe cannot pass thru a wall and cannot be used outside. It will never be waterproof and will rust away rather quickly. You must use class A outside.
 
Thanks

kborndale. I may have misspoken or I might be mistaken...not sure which. ;) I have a double wall stainless steel pipe going thru barn wall. I was told by the guy who installed it, that's what I needed for that application for it not to rust out. This double wall pipe has been installed for about 6 years and it does not have any external rust/corrosion, however I've always struggled with the water leak issue. Is there a way I can tell if this is Class A doublewall? any thoughts on sealing out the water? Thanks again for input!​

 
Hi guys! VERY newbie here, so I apologize for any confusion my post may have in it. I searched and didn't find this answer. I have a pole barn with a woodstove. Verticle 6" stove pipe going up, a 90 going out thru barn wall, double wall going thru barn wall; another 90 going up with a verticle pipe for chimney. To be clear, On the verticle barn wall I have my double wall pipe going thru barn wall to the outside and I have my stove pipe going attached to the doublewall providing my chimney. The double wall pipe sits horizontal (with a very slight tilt out wards/downwards so water runs away from wall); Very typical and simple design I thought! I cannot for the life of me get the double wall stove pipe to seal out water. Seems like the heat of double wall destroys anything I've put around it to seal it....and then I get water in it. Is there a product that makes the double wall watertight btwn the double wall and the barn wall. Is there a heat resistant caulk? gasket? what fits around the double wall to keep water out? any and ALL input is MUCH appreciated! Thank you in advance! - JR
Very atypical and very illegal design. You need chimney pipe through the wall and all the way to the top.
 
Need to clarify - by double-wall do you mean double-walled class A chimney pipe (the shiny stainless stuff) or double-wall stove pipe. The later can not be used to pass through or outside the building. I think you mean chimney pipe. Post some pictures of the inside and outside to verify and maybe spot the issue.