We have the big cousin to your TT. We camp in the low to mid 20's every year. This fall the temp hit about 20 degrees. No issues.
We fill the FW tank full. We do nothing special for the waste tanks. Do nothing for the low point drains or the waste drains.
The tanks are large, and the water has a large thermal mass, so it takes a while to cool off enough to freeze. When water freezes, it freezes from the top down (just like a water puddle).
Keep your city water hose disconnected at night, as it will freeze first.
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