[rollerdawg]

Well it's fireplace season again and my problem is still there. To clarify my situation, I have two fluepipes side by side in the same chimney. One flue is for the water heater, the other for the fireplace. The flue for the water heater consistently goes into downdraft mode whenever it is very cold outside. It acts like a vacuum cleaner and sucks smoke down into the basement from the fireplace flue. To stop this problem, I have to crank up the water heater to create an updraft.

I do have a newer home that is fairly airtight. Your suggestion to provide outside air for the HVAC system might work.

Any other ideas? Is there such thing as an electric heater wrap for the section of flue pipe that connects from the draft inducer to the basement wall? My thought is if I keep the pipe hot enough, the downdraft won't start in the first place.

Thanks!