Expert: James Ball - 2/6/2009

Question
My house is heated by two forced air natural gas furnaces.  My hot water heater also uses gas.  The exhaust gasses for all three combine into one large flue which vents to the outside.  Since both furnaces are powered and the hot water heater relies on convection, I am experiencing "blow-back", instead of rising up the flue, the hot water combustion gasses are occasionally forced back down that flue causing excessive condensation and, conceivably entry of flue gas into the basement.  Should I try to correct this and how?


Answer
Hello Arthur, it is hard to tell what you have from what you describe but it doesn't sound right, yes it should be fixed, I would have a local Certified Chimney Sweep (www.csia.org, there you can look up by zip code to find one near you) take a first hand look at what you have they should be able to help.
James