My furnace is an 11 year old mid-efficiency gas furnace. At the point where the exhaust pipe enters the wall (to go up and out the chimney), I noticed recently that it is dripping water, but only during the time the furnace is working and for a few minutes after it stops. I checked the chimney outside, and it seems ok. I thought that perhaps rain was getting in, but, in fact, it has not rained in days. Moreover, it only drips when the furnace is producing heat and exhausting hot air up through the exhaust pipes. Do you have any idea where the water might be coming from? I will appreciate any comments that you might have on this problem.
Answer:
What you're dealing with is condensation and your service people should take a look at the exhaust system as it can be quite a health hazard. These things are supposed to be installed in a way that all condensate from them ends up outside.
