Hello from a old newbie. This morning my wife uttered the feared "did you hear that?" I listened and figured out that the water heater was the culprit. It is now about 15 years old and probably needs draining/flushing or possibly replacement. However my main concern and reason for this post is... my mechanical room consists of a high efficiency furnace, a water softener and the now noisy water heater. The water heater is natural gas fed, natural draft vented with metal pipe out through the garage roof. This room also has a fresh air intake to supply combustion air to the room. Here is my problem. When the furnace and water heater are both running a the same time the hot gas from the water heater is not venting out but being pulled back into the room around the water heater vent hood and all the hot gas has overtime melted all the little plastic red and blue parts on the top of the water heater... I suspect that this is a "bad" thing. I'm of a mind to just replace this water heater with one that is power vented so this wont happen anymore. Questions ( if I replace the old with a new power vented type) 1. can I use the existing metal vent to run the power vent into? 2. Do I need to supply yet another combustion supply beyond what is already vented into the room. The house is small.. 1 bath in guest bathroom... not used unless guests visit ... My wife and I are only people in the house nowadays. We use masterbath shower. one dishwasher. I think it is a 40 gal heater but may be 50 currently. I am looking for recommendations, comments, directions, suggestions, jokes, good stories.... etc... Thanks in advance.