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  1. #1
    Join Date
    Apr 2005
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    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.

  2. #2
    Join Date
    Apr 2004
    Niantic, Illinois
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    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.

  3. #3
    Join Date
    Jan 2004
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    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.
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