Depending on where you're parked, the layout of the plumbing, and the temperature involved, you may need some 120 V heat tapes and/or insulation to keep your plumbing working in the Winter.
FWIW, ATM, I'm trying to finalize my design for a heated enclosure around my waste tank and drains. I have all of the big parts sorted but am trying to break down the construction of the exit point of the system. It won't do me any good to heat all of the plumbing if the drain caps are frozen or the valves inoperable.