I was told that my venting on the gas water heater does not meet Oregon code. The vent is 4″ in diameter, it goes straight through the ceiling, bends at a 45 degree angle and connects into a six inch microwave oven vent, which then goes straight through the roof. (The 6″ vent was an old stove vent, beofre it was turned into a microwave vent. )
Is it true that this does not meet code in Oregon?
I doubt that it is legal anywhere. You cannot vent a gas burning appliance into a fan duct. By doing this you have provided an easy way for carbon monoxide to enter the house. Since flue gases depend on their heat to rise out of the chimney, a long flue can cause them to cool sufficiently so that they will begin dropping down the flue. If the flue is installed into a fan duct, they will then drop into the living space and create a life threatening situation. This condition would also occur if there were a central attic fan in the house which could create a negative pressure in the residence, drawing the flue gases down the duct.