Why would your hot water heater leak from the top as opposed to the bottom? To help answer this question, we took a 16-year-old water heater that we replaced for a customer and cut the top off so we could show how a leak from the top could occur. The joints for the exhaust vent and the two ports that connect the water lines are all-welded by the manufacturer. If there’s a leak from the top, it probably indicates that one or more of the weld joints for the connective ports has failed.