Upon inspection of the 30 gallon gas heater in a rental I found that the inlet line and the exit(hot) lines are hooked up in reverse. They appear correct but when hot water is used in the house the pipe connected to the cold water inlet on top of the tank heats up. That is, the water flows in reverse. It has been this way for years and no one has complained.
Obviously I intend to correct this but wonder just how this backward flow affects the gas use and/or the efficiency. I also wonder just what idiot did this installation, but I doubt that I will ever find that out.
Anybody else ever found this? Comments are appreciated.