Dick_B wrote:
The argument against the drain valve is that it has to be removed to flush out the crud that collects inside the heater.
Of course, the crud does not have to be flushed out but the heater works better. Same as the water heater in the stick and bricks house.
If your water is clean enough very little Crud collects in the water heater. I realize in a camper where you are going all over the country you don't have much of a choice to how good the water is.
In my home the Rheem Marathon electric water heater that the power company installed for free has no drain plug on it to let the crud out.