DrewE wrote:
As others have said, "heated tanks" quite often means merely that they are (minimally) enclosed and insulated and there's a small duct from the furnace into that space.
So long as you use the furnace for heat (as opposed to, say, electric space heaters), this is generally sufficient to keep them from freezing in at least moderately cold weather use, and certainly far better than tanks hanging exposed to the elements. It might not be sufficient for 20 degrees below zero weather. Not many mass-market RVs are set up for bitterly cold weather from the factory.
Our 5er had enough ductwork to keep the tanks from freezing; but in our case, the pipes leading to the main dump tube were still exposed.