Installing a liner in an existing utility chimney

[wendell]

I am using my existing utility chimney (8" round clay tile lined surrounded by concrete block) as the container for the 6" liner for my woodstove which I am installing in the basement of a 2 story house. I will be cutting into the utility chimney on the opposite side from where the existing hole is from the former furnace. In talking with the installer, he wants to leave the bottom of the liner T in the utility chimney unplugged to make cleaning easier. This certainly will as all I will need to do is open the clean-out door on the utility chimney to remove what has been cleaned out of the liner.

The concern I have is that all of the smoke, especially on start-up is going to go into the T and up the chimney and none of it will spill down through the open end of the T. I'm also concerned that although the existing hole in the utility chimney will be capped that there might be enough air leakage through it or through the door on the clean out to affect the draft.

Am I worrying about nothing or is there a better solution that what he has proposed? The clean out door is quite small but I did wonder if it would be possible to reduce the bottom of the T down to 3" and extend it down to the level of the clean-out and cap it there so system would be sealed and the cap could be removed for cleaning.

Should there also be any concern of loss of structural integrity added a second hole into the existing chimney? I can't wait to install my new stove but having the chimney collapse inside my home would be a high price to pay!

Thanks for your help!

 

[jbrown56]

Wendall, First, if you seal the old thimble with brick and mortar, your chimney should be fine. Make sure to cut the new thimble opening a little larger to give a little extra room to work. I don't think it is a good idea to leave the bottom of the liner open ended because you will be letting air from the existing chimney and clean out into the new liner and may upset the draft. You can always clean the liner at the thimble. Hopefully there won't be much ash to clean anyway.

Jim

 

[webbie]

If there are air leaks into your existing clean out, this could slightly cool you chimney. Make certain it is tight - even if you have to throw some temporary caulk on there each time after you clean.

If you find that the "sump" impedes the chimney draft, open the cleanout and stick a wad of insulation up there (fire proof - and also keep it well below where you tee snout is).