I have a rental gas water heater that will be orphaned with the installation of a high efficiency furnace.
I have been told by one HVAC contractor that I don't need to get a liner for the chimney if it's 'within 1 size'.
Other contractors are recommending a 4" liner.
The outside diameter of the flue pipe is 6" (by my measurement).
What would the inside diameter be? - is it 5" inside?
Is it small enough to be withing 1 size or do I really need to get a liner installed to prevent condensation damage in the chimney?
Thanks for the help.
A wary consumer.
Go with the 4" liner. In my are it's code. Beyond that with a 6" flue it will tend to have a long wet cycle, this means it will condense. On a wiindy day or with the right barometric presures or even the right temp difference from the chimney to the outdoors it may want to backdraft into the home.
Your local code may require the liner, but the national code permits a 3" barometric to be vented into a 49 sq. in. chimney.
If your chimney is 6" od, you are well under 49sq. in.