anode rod

You might try cleaning the threads on the water heater with a small wire brush. Corrosion can build up enough to make it hard to thread the rod. When we store the RV for the winter, we clean the threads, put a light coat of vaseline on the threads, and then put a clean cloth loosely in the hole. This keeps bugs, etc out of the water heater and keeps the threads from corroding. When we reinstall the rod in the spring, we start it with our fingers, then tighten just enough to snug it with a socket. We also use a wrap of teflon tape on the rod.