A co-worker of mine (with a SOB) left his water running in the kitchen sink recently. He had his gray tank valve open, so as not to fill the tank and just let it drain as it trickled. He had no heat trace nor insulation on the drain line outside...it froze, the tank filled, the sink overflowed , and he awoke to a helluva mess! Same guy bought a couple of gallons of the pink RV anti-freeze - while here in Wyoming, preparing to winterize upon his return to Utah. A couple of days later, in the back of his truck, both gallons of ANTI-freeze were frozen solid as rock!
This being said, I've had no problems (knock on wood) with anything freezing on the CYCLONE! While adding the insulation underneath, I do remember seeing the lines from the tank running through the frame and touching the steel. I suggest adding a skirt; it keeps the cold wind out from the bottom near the lines. And, if you're gonna make a habit of extreme cold weather camping, drop the underbelly and add insulation! Works for me!