<https://www.inspectorsjournal.com/topic/16195-water-heater-vent-near-wall-fan-assisted-draft/#comment-135677>
<http://schema.org/text>
"You are correct where there is a wall within 8 feet. I really never see that case since almost every B-vent I see is in a sloped roof, where the height is based upon roof slope.      Unlike fan assisted furnaces that still rely on chimney draft, all of the fan assisted water heaters I see are positive pressure and should not vent to a B-vent. \n"
<https://www.inspectorsjournal.com/topic/16195-water-heater-vent-near-wall-fan-assisted-draft/>