Thimble/Stove Pipe fit

Purchase a thimble from the company that you purchase your pipe from. You shouldn't be mixing/matching UL Listed Class A components. Thimbles are made to ensure Clearance to Combustibles are met and since different companies have different CTC, you could run into trouble using a different companies pipe on your existing thimble.

If you are just running black stove pipe into the thimble, the manufacturer isn't all that critical as single wall stuff is pretty standard. I would suggest filling the space with a dab of stove cement. If you can, try to get some screws into it as well. Watch the length - it should be long enough to reach the chimney, but not so long that it sticks into it.

Gooserider

Gooserider said:

I would suggest filling the space with a dab of stove cement. If you can, try to get some screws into it as well.

Gooserider

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Emory,

I can tell you from experience that the cement won't hold too long. It will likely crumble and leave gaps. On the stove in my shop, the best thimble seal I got was by stuffing door gasket (the rope) into the thimble, around the pipe, THEN troweling in the cement. It cracked less because the gasket supsended the pipe, and when it did crack, I still had a seal.

I'm assuming the thimble itself is mortared into the chimney opening. The issue is then the connection of stove pipe to thimble. Best way in my experience to do this is with a short length of double male ended pipe - crimped at both ends. You can buy these ready made or make them with a crimping tool (a stove shop should be able to do this for you). Heavier gauge pipe will usually make the fit tighter. Furnace cement tends to look unsightly and will deteriorate rapidly.

emory said:

So your saying the pipe should go a decent way into the thimble. Right now it only goes about 2" into the thimble.

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Yes... Essentially it should ideally go in the exact depth of the thimble so that the edge of the pipe is even with the edge of the chimney. The increased length gives more area to seal so you'll have a tighter fit just from friction alone, it will stay a bit cleaner, and will tend to stay together better - even if the pipe wants to back out, it has a lot farther to go before it causes a problem.

You will see this in just about any stove manual where they talk about connecting to a chimney through a thimble.

Gooserider