Gas Furnace problem
My Lennox high efficiency gas furnace model G14Q3-60-C6 has been working great for 18 years. Yesterday I noticed condensation on the outside top surface of the "Flue" Attenuator, (exhaust muffler?) The condensation seems to be dripping from the PVC exhaust pipe joint where it connects to the Attenuator pipe. This has never occured before so I checked the condensate drains that are attached at the "drain leg assembly" and all is clear and the water drips freely when the furnace is running. I am thinking that the PVC glue joint must have a small defect (opening or crack in the glue?) that has just recently opened up, causing a small drip of condensate, since it only occurs while the furnace is running. The intake attenuator and associated PVC piping are fine, there is no condensation forming anywhere on that system. Is it possible that the Attenuator is full of water? Thanks for your help.