I live in Washington State (eastern), and have had my Jayco dealer winterize my Greyhawk 3100SS. All they do is blow out the lines, drain and by pass the water heater, leave the low point drains open and pour about a gallon of RV antifreeze in the sinks, shower and toilet. No antifreeze in the water lines. So far no problems. I do keep my RV indoors, but unheated, so probably does not get as cold as it would parked outside.