I too just keep a space heater on low or use a cube that turns it on at a certain temp. Open the lower cabinet doors etc. I don't see much point in leaving a full water tank. Drain it some to allow for expansion if it does freeze. Old trick from my Alaska days.. Use windshield wiper fluid instead of anti-freeze. Cheaper. But not if you drink out of your water tank. Often our only source of water up there was lake or creek water, so we didn't drink it without boiling. One year here in WA I had everything set up but the power went out for days and the temps dropped to almost 0. I couldn't get to the RV to do anything. Busted my hot water tank wide open, yet all the lines were fine.
