Ever seen a proper water heater vent installation? Let’s explore our findings on this particular inspection.
Upon entering the attic, the Inspector was observing all the vent extensions through the roof. Upon a closer examination of the water heater vent, it was discovered the vent was not of a proper material (rather a downspout) was encased in another vent (second row photo). Also, it was not installed properly and there was a gap between the two sections and thus releasing carbon monoxide gas into the attic air as well as the potential of entering the home as well. The larger (female) section should be sitting on the smaller (male) section. The vent was also touching the wood next to it. Not only is this improper, it is unsafe as the heat from the vent could cause the wood to become combustible with the carbon monoxide gas.
Water heater vents should have the right type of B-gas vent, which are usually rounded, fit into the water heater vent diverter, and extend through the roof with a 1” minimum clearance around them with female end seated on male ends in the direction of flow. There should be no gaps in the venting of gas appliances. 
Solution: Install the correct type of vent per manufacturer’s instructions and recommendations for the water heater and have it extended through the roof, where it is sealed at the roof jacks. Vents going through the roof should also have a 1” minimum gap between the sections and the decking and other combustibles.