I have 2 appliances - furnace (forced air) & hot water heater (no fan) that vent through my chimney. I recently had a repair performed on my furnace and the technician noted that my venting was installed incorrectly. Specifically, she said the wye connection should have been installed on outside of the chimney NOT within the chimney itself (see pics). I cannot recall her exact words but she said this setup would make it difficult to determine the condition of the chimney liner itself which could become an issue down the road.
Please have a look at these pictures. Do I have a real issue here?