How to replace crock (thimble) ?

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  #1  
Old 04-02-19, 06:48 AM
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How to replace crock (thimble) ?

The clay "crock" that goes through our basement wall (Superior walls) is cracked and broken in several places. I'd like to remove it and replace with double wall metal or satisfactory equivalent. We have our wood/coal stove piped into it. It is about 30"-32" inches long.

If I break off/remove the visible cement blocks that support the crock, will that allow me to pull the crock back into the basement? There is a clean out door on the exterior, but it is small and doesnt line up as well as it could.

The vertical black pipe in one pic links the stoves air jacket to a return vent. Not a flue gas vent.

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Last edited by PJmax; 04-02-19 at 08:49 PM. Reason: cropped/reoriented/resized pics
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Old 04-02-19, 06:59 AM
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It looks like a piece of terracotta or cement drain pipe. I would replace it with something similar as mortar will bond well with it. I assume yours cracked from the heat of the flue. When you replace the pipe go to a larger size. Then when you reinstall your flue center it in the pipe and fill the gap loosely with fiberglass insulation.
 
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Old 04-02-19, 07:19 AM
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I've always heard it called a thimble and generally they are made of terracotta. I'd also replace it with the same.

 
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Old 04-02-19, 11:59 AM
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OK. All good advice. Now get me started on removal of the old clay pipe. If I chisel away at the blocks/mortar surrounding the clay pipe, will I be able to loosen the clay pipe and pull it inwards to the basement? The blocks supporting the clay pipe are freestanding but against the Superior wall. Not part of the foundation at all.
 
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Old 04-02-19, 12:09 PM
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It shouldn't be hard to remove. Here is an example of a thimble - https://whiteheadindustrial.com/clay...EaAijtEALw_wcB
 
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Old 04-02-19, 08:52 PM
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Since that's slid in from the inside.... it only has cement on the face. It will come out easily.
 
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Old 04-03-19, 04:47 AM
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When chiseling the mortar use more lighter hammering/chiseling hits. Don't go crazy and beat on it hard as you risk breaking the CMU blocks or their mortar joints. If you have a cordless hammer drill you can also use it as a mini jack hammer. It's fine hits/vibrations are good for breaking up mortar by drilling a series of shallow holes and using it a bit like a jack hammer to help chisel off the mortar.
 
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