What is a flue liner and when do I need one?
A flue liner is a flexible metal liner that is pulled down your existing masonry or clay tile chimney. The flue from the furnace and water heater vent into this liner. This prevents water vapor from condensing on the surface of your old chimney and deteriorating the chimney. Liners are needed when venting an 80% efficient furnace into an older masonry or clay tile chimney.
