My Springdale TT did not have a manual switch, but it did have an automatic switch over. I never let it actually work though, because I deliberately kept one tank turned off. When it emptied, I'd turn it off and turn the other on. (no switches, just the knobs on the tank). I wanted to know one tank was empty and needed refiling. If both run automatically, you never really know when one is empty, until BOTH are empty and then, at 2:30 AM when you wake up to a cold camper, it's not fun with no heat! Manually turning on the full tank, you might have to get out of bed, but at least you'll be warmed up again in a few minutes. Then you know you've got a little time to get the empty tank refilled.
I did try using the automatic "thing", and one tank did empty first, then the other, they never emptied equally at the same time.
My current trailer has a manual switch over. But I still keep one tank turned off at the knob all the time and fill the empty tank as soon as it empties.
