condemsation in flue

New Brunswick, Canada   

My furnace creates water which lands in the clean out.

The flue has a brick liner which is 10 by 10 I put a 8 inch s s liner in side the liner.

The flue did not always have condensation in it. The flue is 35 years old


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by ChimneyChick | October 29, 2015 ChimneyChick's avatar
Midland, Ontario

Hello New Brunswick.
The condensation is because the hot flue gases mix with the cold air /steel liner and makes liquid…I would have utilized an insulated chimney liner in order to keep the flue gases warm…I assume this is a natural gas furnace??
If someone did the math and took the BTU output of the furnace and calculated to the Height of the chimney you may have found that the 8” is too big and a 6 may have been better. Your furnace people should have been able to advise you on this calculation from the Oil or Gas codes

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