chipmunk. It is not mandatory, however when transporting a hws on its side the anode will flop about within the cylinder & chip the vitreous enamel, the anode can also break off at the thread, thereby rendering it useless. Your warrany will be shot & you will become impotent. If you have to transport the HWS in the horizontal position – remove the Anode & replace it when you get there. Bob
Hello Bob. Thanks for your reply. This is a 2 element water heater and assuming that the most likely damaging forces would be verticle (ie, bumps in the road). Since the elements are mounted into the side of the tank, laying the tank on it’s side with the element covers pointing up would make them less vulnerable. Just a thought. Everyone I know of that has a pick-up, has a camper shell on it, making it impossible to stand the water heater upright.