As you can see an installer changed-out low to high efficiency furnace, but failed to run an exhaust out. Instead he reconnected a PVC pipe to the old sheet metal exhaust! As a result the sheet metal fittings and pipes will rust out in no time, at first clogging the drain, and then it will create holes!

It’s like they built the house and when they were done said “$hit, we forgot about that furnace thing. Just put it outside and run the air pipes up the wall. Now where’d I set my beer?”