Michelle -
I'm terrifically disappointed! As a lifelong Mainer, I was thrilled to have you aboard. There aren't many of us. Well, East Tennessee (Knoxville, maybe?) is a beautiful area. And it seldom hits 30 below, as inland Maine often does!
Black tank = toilet contents. Gray tank = everything else (sinks, showers, etc). In a TM, the gray tank is below the floor, exposed to the outside temperatures. The black tank is built into the toilet, and is inside the trailer, so it won't freeze while the bathroom is warm. The drain valves for both are outside the trailer, located at the dump hose connector behind the left wheel.
If you dump the black tank (potty contents) into a portable tank ("blue boy") each time you leave, you should be OK. Bear in mind that if the temp is below freezing, the dump valve may freeze shut, so before leaving you need to plan enough time to thaw it out with a hair dryer on your generator. But while you are in camp, do NOT leave the dump valve open so that the toilet drains directly into the blue boy. Very bad idea (Google "rv toilet black cone").
Finally, and a little off topic. We have been discussing the toilet. But beyond that, if the trailer will be unheated in freezing temperatures, you must be sure not to allow any water to get into any of the fresh water plumbing, since damage will result if it freezes. There is a "winterizing" article here - take a look through it.
http://www.trailmanorowners.com/foru...272#post139272
Bill