Recently I've noticed water gathering around the base of the exhaust pipe. I've wiped it away and watched it slowly accumulate around the base, as if it's coming from the coupling of the pipe to the furnace itself (not from some exterior source). The screws holding the coupling to the furnace are rusting, so evidently this has been happening for a while but I just noticed it recently.
Any ideas as to why this might be happening? Should I just apply a sealant around the pipe where it joins the coupling? Thanks in advance.