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What kind of chimney would require a SS liner with a natural gas furnace

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What kind of chimney would require a SS liner with a natural gas furnace
asked in Heating System by joe-b (120 points)
edited by darekrudy
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1 Answer

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Hi Joe,


I’m not sure if I understand your question correctly. All types of masonry chimneys (stone, brick, cinder block, etc.) currently require liners, but they do not require stainless steel liners. On the other hand, some of the gas burning appliances require stainless steel vent pipes, and if such appliance discharges through the masonry chimney, stainless steel liners. So, it’s the matter of matching the appliance’s venting requirement. 
In other words, if your natural gas furnace (or boiler) requires stainless steel vent pipe (most likely due to acidic condensation) and if you have a masonry chimney, you need to install a stainless steel vent connector between the furnace and the chimney, install a stainless steel liner inside the chimney to prevent its deterioration, and connect both in such way that it prevents condensate leakage inside the chimney. 
answered by darekrudy (21,730 points)
Thank you for this answer. To refine my question, my chimney is 50 years old and made of brick. But, it is lined with square, clay flue pipe.

Do I have to line the flue with stainless liner?


Joe B.


Hi Joe,
I don't know if your furnace requires stainless steel vent or not. If it says in its manual that it does, you need to install stainless steel connector and stainless steel liner (even if the clay tile is in a good shape). 
If the furnace doesn't require stainless steel venting you need to make sure that the existing clay tile is in a good shape: not deteriorated / falling apart  / crumbling, and that it is proper size to vent this appliance. If it shows significant damage, there are exposed bricks inside the chimney flue (you might need a professional to evaluate the chimney), you will need to install new liner inside. However, it does not have to be stainless steel.
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