Questions on Chimney Cleanout Installation

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Nov 19, 2021
6
Western NY
Good Day. I'm running into a few issues getting ready for the heating season.

A bit of info on the setup: We had our wood stove installed a few years back. The chimney is piped out the back of the Hearthstone Heritage stove horizontally and through the brick hearth wall into an external masonry chimney. Inside the vertical masonry chimney is the original 9x13 terracotta liner from the original woodstove build from the 80's. During the updated install 3 years ago, they added a single walled 6" stainless horizontal pipe to a tee then a 6" flexible pipe up the liner to the top. Around the flexible pipe was backfill with Thermix Insulation.

I have always cleaned the chimney from the top down and needed to disassemble the inside of the stove in order to gain access to the horizontal to use the shop vac to remove the spoils. This is necessary since there was no clean out on the chimney accessible and moving the soapstone stove is not an option. I realized after the first cleaning that the failure to have the installer provide me a clean-out when they installed the stove was a mistake. I didn't know then what I know now.

While cleaning the chimney this summer, I dropped my brush and 2 extension rods down the chimney (DOH!). I have always intended to add a clean out but put it off every year since. This accidental drop of the brush has forced me to do it now since I needed to get the brush and rods out of the chimney.

I measured carefully and cut through the cement and terracotta from the exterior and exposed the bottom of the tee. I removed the round bottom of the 6" tee and retrieved my brush and rods as well as cleaning out the spoils (much easier by the way than going through the stove). However, now I have a problem. When I went through the cement block and terracotta liner, the Thermix also came dumping out. I was able to cleanly recover most of it and have it stored in order to reinstall it. However, I'm not sure what to do about the cleanout area and how to address the issue with retaining the Thermix. If I close the cleanout door and simply pour the Thermix in from the top, I'm going to have the same issue with the Thermix the next time I clean the chimney when I open the clean-out door.

I'm sure there is an easy answer to this but was hoping to get some advice. I'm handy and fairly intelligent, but not the most knowledgeable with wood stoves & chimney design. Is there a product or method I can use around the tee to retain the Thermix above and around the tee but still allow me to access to the tee clean-out on the bottom? I've included a picture for reference. (This photo was before I cleaned up the opening in preparation for the cleanout door).
[Hearth.com] Questions on Chimney Cleanout Installation

Thanks for any advice.
-Jason
 
Maybe get a top plate and cut it down to fit? Attach with L brackets, then cement it in?
 
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I would stuff solid rock wool insulation around the top of the access hole to hold the other insulation up. You will have to find a product that can handle the temps, a mechanical insulation or commercial HVAC outfit might be able to help you with a suitable product.
 
Spent the weekend doing some research on my issue. Learned a lot.

It appears that my problem stems from the installation NOT being done properly. The installer did NOT mix the Thermix with water before they filled the flue around the new 6" flexible liner. It was filled with dry Thermix. As a result, the Thermix poured down from the clean-out I opened in the bottom of my cement/clay flue. It should have been cured rigid and held in place if installed correctly.

So, my plan is to uses some sheet metal to make a two-piece collar to wrap around the tee at the bottom of the liner and install new Thermix, using the correct method, around the liner. Not looking forward to paying for the Thermix a second time or the work ahead, but I guess getting it done correctly is more important.
 
Bummer, but it is good you are getting this fixed properly. To be done correctly the liner needs to have spacers attached which maintain at least 1" clearance from the clay tile so that the Thermix can fully surround the liner all the way down. Did they do this?
 
Bummer, but it is good you are getting this fixed properly. To be done correctly the liner needs to have spacers attached which maintain at least 1" clearance from the clay tile so that the Thermix can fully surround the liner all the way down. Did they do this?
I do not know. I will try to find out. I haven't been back onto the roof to look down the chimney since the insulation was removed from the clay tile.
 
Spent the weekend doing some research on my issue. Learned a lot.

It appears that my problem stems from the installation NOT being done properly. The installer did NOT mix the Thermix with water before they filled the flue around the new 6" flexible liner. It was filled with dry Thermix. As a result, the Thermix poured down from the clean-out I opened in the bottom of my cement/clay flue. It should have been cured rigid and held in place if installed correctly.

So, my plan is to uses some sheet metal to make a two-piece collar to wrap around the tee at the bottom of the liner and install new Thermix, using the correct method, around the liner. Not looking forward to paying for the Thermix a second time or the work ahead, but I guess getting it done correctly is more important.

Full disclosure here...
I run a custom sheet metal shop and have access to pretty much free sheet metal, CNC plasma table and all sorts of helpful equipment, I would still fill around that tee with a solid rock wool insulation. I feel trying to secure a sheet metal collar no matter how many piece is going to be a pain and you will still have gaps to fill.
Merely my ¢.02