How do you seal a wood stove exhaust pipe?

[Alaskajohn]

The wife got a little aggressive in cleaning the wood stove exhaust pipe where it leaves the wood stove. On close examination the exhaust pipe fitting was “customer made“ by the original homesteader and the wife bent it a bit when she removed it from the wood stove. I’ve tried fixing as best I can but there is up to a 1/8 inch gap in spots. In fitting this custom made exhaust pipe back onto the store bought exhaust pipe, there are a couple screw holes exposed now as I wasn’t able to get it to fit back on the way it was originally installed. I am sure it will be leaking smoke from these locations if not fixed.

Googling this issue shows caulking to be the typical repair method. Does anyone have tips on if there is a tape product made for this high temperature situation. I could certainly caulk it, but was wondering if there are viable alternatives or additional applications to caulking.

I will need to fire up the wood stove in the next week or so as low temps will likely be in the high 30s before the end of August.

Any advice from knowledge folks on this would be appreciated. Thanks

 

[Sourdough]

Here is tape for up to 1,000 degrees. Might call "Alaska Industrial Hardware"
https://www.bing.com/search?q=high+...c=10-21&cvid=5777c851b3c14057ab1a02adff0dd97a

 

[Caribou]

Red RTV silicone. Red is the highest temperature and I have used it on wood and oil fired appliances for years when I had my heating business.

 

[Caribou]

Here is tape for up to 1,000 degrees.
https://www.bing.com/search?q=high+...c=10-21&cvid=5777c851b3c14057ab1a02adff0dd97a

I've had excellent results with the foil tape but I'd fill in the big gaps with the RTV before taping over.

 

[Alaskajohn]

I've had excellent results with the foil tape but I'd fill in the big gaps with the RTV before taping over.

Thats kind of what I was thinking.

 

[Alaskajohn]

Here is tape for up to 1,000 degrees. Might call "Alaska Industrial Hardware"
https://www.bing.com/search?q=high+...c=10-21&cvid=5777c851b3c14057ab1a02adff0dd97a

I will be in the valley all day and I think they are open. I’ll stop by.

I just checked the weather forecast and we should have lows in the high 30s by the end of the week.

 

[Sourdough]

There are also several shops in Anchorage that make custom sheet metal products. Maybe next summer have a new adapter made (or two adapters).

 

[Caribou]

I will be in the valley all day and I think they are open. I’ll stop by.

I just checked the weather forecast and we should have lows in the high 30s by the end of the week.

AIH, Home Depot, Lowes, Spenard Builders should have what you're looking for. I often got my RTV at an automotive parts store.

 

[Magus]

I used this myself, and its stronger than paint!

Cut the top and bottom out of a quart juice can and cut along the seam with tin snips and clip it around the leak and using stainless steel hobby wire (bailing wire.) wrap it three times around the top and bottom, twist the ends tight and nip it off. works on tailpipe repairs too.

Alternatively, use a spare piece of stove pipe or sheet tin and spray it with black motor paint.

 

[Alaskajohn]

When I was in town I stopped off at a store that sold and installed wood stoves and picked up a tube of Mill-Pac Black. It’s what they use on their installs. Specifically made for this purpose. Rated for 1050 F. Worked perfectly. No need to tape. Only issue is the product has a one year shelf life and cost $28 for the tube. That kind of sucked. It’s has gotten down to 36 degrees, so just in time!

 

[SLADE]

Put a screw in the screw holes and put furnace cement in the gaps.

 

[Aerindel]

A properly constructed chimney system is always under NEGATIVE pressure and only ever pulls room in air IN through gaps in the chimney.

A system that counted on any kind of seal to work, would be very dangerous as any crack or leak could fill your house with carbon monoxide. If you ever have issues during normal burning of smoke coming out through screw holes or pipe joins, stop, clean your chimney, redesign it, etc. Simply closing the gaps is not solving the problem and putting you in significant danger.

I am very serious about this. This is not one of those "crazy Aerindel opinions" that you can take or leave, but stone cold laws of physics kind of things.

Luckily, if you have a decent draw, this isn't something you should ever have to worry about and only need your chimeny to seal well enough to keep drawing, rather than to seal anything in it. I've heated exclusively with wood for my entire life and never once needed any kind of sealant on my chimeny pipes. All my pipe sections just loosely socket together and only smoke if something has gone wrong, like a chimney fire or blocked chimney or freak gust of wind causing a back draft.

This is not to say, that its not better to have a tight chimeny, it is, mainly because leaks in the chimney let room air escape your house, and reduce the draw from your stove, but never count on them to keep smoke out of your room, the seal is to keep the room air out of the chimney.

 

[777funk]

And with stove pipe (real 6", 8", or 10" diameter) being cheap enough and readily available, there's no reason to have the indoor sections of stove pipe being home made. It is actually supposed to be UL approved. Same goes for the double or triple wall sections that go through the attic or roof. If you have homeowners insurance, UL approval is required. If you don't worry about that, you at least should be very sure that the home made pipe is big enough diameter for your stove and solid enough that it won't fail. I would just spend $100 (probably less) and buy whatever indoor sections of stove pipe you need. They are UL approved which means it should work safely if it meets the stove's and install's requirements.

 

[Woody]

I used Rutland Stove and Gasket cement when I rebuilt my 1800’s cook stove. As I remember, it would stick to about anything when cured. Came in a caulking gun tube, but had smaller hand squeeze ones also.

Stove Gasket Cement

And with stove pipe (real 6", 8", or 10" diameter) being cheap enough and readily available, there's no reason to have the indoor sections of stove pipe being home made. It is actually supposed to be UL approved. Same goes for the double or triple wall sections that go through the attic or roof. If you have homeowners insurance, UL approval is required. If you don't worry about that, you at least should be very sure that the home made pipe is big enough diameter for your stove and solid enough that it won't fail. I would just spend $100 (probably less) and buy whatever indoor sections of stove pipe you need. They are UL approved which means it should work safely if it meets the stove's and install's requirements.

All well and good when fittings are 'standard' size. You get into custom made stoves or the early 1800's or earlier stoves, not everything is a standard size. I have helped on some stoves that needed custom pieces made.

 

[sonya123]

when we first moved to this property we hired a professional chimney cleaner and repairer, and it was a good thing too. The one in our kitchen didn't even have a liner the living room one had gaps in the stove pipe. If we had used it as is we could have died from carbon monoxide or caught the house on fire. It did not cost a huge amount to get it all fixed and we now have him clean them once a year. Maybe look for someone that can fix it right ?

 

[Alaskajohn]

Thanks everyone, but it’s fixed.

 

[777funk]

Thanks everyone, but it’s fixed.

Good. I would still use caution and recommend replacing with official factory made stove pipe if you have homeowner's insurance. Most (or all) insurance companies will require UL approved pipe for wood stoves. As such, I'd doubt they'd cover a house fire in a house with home made stove pipe. They're in the business of making money and look for legal ways out of paying. That's a legal way out in their mind.

 

[Alaskajohn]

Homeowners isn’t an option where I live. I did visit a shop that does this for a living and there will fabricate a fitting for me. A standard pipe will not fit the woodstove opening. I was able to reshape the fitting and I had it down to about a printer paper space in on location, and their was more than adequate surface for the woodstove caulking.

 

[havasu]

Marty from Homestead Rescue lost a house in Alaska himself when he failed to use a double walled stove pipe. The outer pipe should not get so hot that a neoprene jack boot wouldn't work well.

 

[777funk]

Marty from Homestead Rescue lost a house in Alaska himself when he failed to use a double walled stove pipe. The outer pipe should not get so hot that a neoprene jack boot wouldn't work well.

The outside of double wall gets about 800F when the creosote inside ignites (chimney fire). You can't touch the outside of the pipe even for a split second it's so hot. Double wall isn't required for the indoor pipe in most cases if clearances are large enough (I believe it's usually 18" from a wall or more). I can't imagine how hot single wall would get (I have double wall inside the house).

But point is, building code and UL spec on wood stove piping is there for good reason. There needs to be plenty of space between the hot pipes and the wood framing or other flammables in the home. This is why they require what's pictured below for wood stove installs and the acompanying supports where it passes through the ceiling and roof.

It gets hot when (not if) there's a chimney fire. I believe the stove pipe that passes through the ceiling is rated around 1500F plus minus a couple hundred degrees. It needs to be rated for those temps to keep the structure intact. I sweep the chimney twice a winter and still could get a chimney fire if I wasn't careful. I'm not sure what the in house connecting stove pipe is rated at but I would guess it's also pretty high temp stuff.

 

[havasu]

Thank you for this clarification. I just remember Marty emphasizing the necessity for a double wall exhaust. Creosote fires are usually from burning junky pine wood, and other sappy types of wood?

 

[777funk]

Thank you for this clarification. I just remember Marty emphasizing the necessity for a double wall exhaust. Creosote fires are usually from burning junky pine wood, and other sappy types of wood?

I burn only hardwood and the flue always has a coffee can worth of black crystalline creosote that can be removed (brush) after a few months of steady burning. If you always burn full throttle wide open air, it may make less creosote but I still see having to brush the flue a regular requirement. I can shut down a chimney fire pretty quick by closing off the air to the stove. Leave the door open too long with a hot fire and it's sure to get out of hand fast if there's anything in the chimney. Not a good idea anyway to leave the door open on a modern wood stove. Way too much air and the fire gets huge fast.

 

[Aerindel]

Well....a reason to use homemade is that nobody sells stovepipe as good as what I can make, 1/4 thick steel....and about half the cost of the 20 gauge crap you find in stores.

Single wall running through the middle of all three stories. I reclaim a huge amount of heat that way.

 

[Aklogcabin]

Actually you need triple wall through any openings. Class A. As I'm not building it's expensive. 500 bucks for 4 foot. I also use double wall in home and remote cabin. My family is sleeping there.
Single is OK. Inside. And quality is all over. I believe that the stainless steel I good. Thin black wall pipe is cheap in several ways. I won't use it around folks. Garage n outbuilding great. Not in a living area. Folks do it I don't.
Yeah John. That's what I have used. Bought it from Dan the fireplace man. Great guy, tell him your needs n watch a professional design what you need n have the best quality. On hand always available parts.
Eh folks he's an Alaskan

 

[Aklogcabin]

Hey ak John how you getting by ? Lives great here. Hanging out with grandkids and a real pretty lady. Going out to start the 59 case backhoe and plow some more.
3-4 snogos to fix. Grandson, just 6 got a great compound bow so we can practice. Cabin is great I guess. The 6 wheeler at the lake probably not so much. Under 7 foot of snow now. Bears have a ball eating wheelers. Should start a board n have squares. How chewed up can bears damage a 6 wheeler. You'll have that, emergency evec

 

[Alaskajohn]

Hey ak John how you getting by ? Lives great here. Hanging out with grandkids and a real pretty lady. Going out to start the 59 case backhoe and plow some more.
3-4 snogos to fix. Grandson, just 6 got a great compound bow so we can practice. Cabin is great I guess. The 6 wheeler at the lake probably not so much. Under 7 foot of snow now. Bears have a ball eating wheelers. Should start a board n have squares. How chewed up can bears damage a 6 wheeler. You'll have that, emergency evec

I’m living the dream, thank you! We don’t have 7 feet of snow, probably 5 plus feet, but I stopped counting. It’s been a very quiet winter with my only year round “neighbor“ wintering someplace warm for the first time of his life. The snow has been tough on my snow removal equipment and I am down to using my backups. I need a D4 dozer I think. The cabin is my rock star. Happy that I invested to put a basement under it and now I have running water, plumbing, washer and dryer. Makes the wife happy and no more -40 midnight dash to the outhouse.

 

[Aklogcabin]

Yeah I rented a 4x4 backhoe. Got to minus 25s n would not start. I had to pre heat and just let it run. Took me 4-5 days to get all pushed back.
I'm on backup also but gaining back. Hour to fix snowblower. Now the 4 wheeler plow doesn't work, probably another hour fixed that. Near ready to drop the tyranny on my plow truck n replace the 9 $ seal on the torque converter. And replace the converter n seal. Reinstall the tyranny. Just have to shovel 3' of snow around it first. Outside job.
My 59 case backhoe should fire today. Been plugged in n battery charger on for a couple days now. Need to plow some more.
Then we should be back to full power Cap'n.
Heck I've been trying to get some heat into our new home we're building. Going to move a wood pellet stove in to it, temporarily

 

[viking]

If it's raining hard I sometimes get the creasote in the chimney burning to clear the build up, closing the stove doors and closing the air supply adjusters tight limits the stack to burning intensity. One thing I did when I built our home was that I used fireproof marine board (I think it's made of magnesite and is nearly as fire resistant as asbestos) it covers the rafters all around where the chimney goes through the roof, so even though the outside of the metalbestos gets extremely hot, the rafters never get hot enough to char. I will say that seeing all the flames from creosote burning still makes me nervous, anyway I do the best I can to keep the stack from burning violently. We do have a stack brush, just haven't used it yet.