I am a firm believer in draining the water from the water heater between trips, but on top of that, you must remember to check the anode rod every couple of months. This is a rod in the bottom of your heater designed to corrode so the tank itself won't. It looks like nothing more than a 1 1/16th inch plug. Anyway, if you were to leave the water in the tank, the rod will only corrode that much faster and eventually the corrosion will then eat up the water tank. By draining the tank after each use you can monitor the anode rod for replacement if necessary. The rod only costs about $10. 00, and if you go to the Good Sam RV website, I'm sure you will find more on this subject.