We travel mostly in the Winter with temps down to, and occasionally below, zero. We only hook up to shore water and sewer to empty our waste and fill the fresh water tank again.
We do not use our furnace very often and rely on electric heaters for comfort. If it looks like it is going to be below freezing, we have a thermostatically controlled incandescent light that will come on in the wet compartment that has always prevented any frozen pipes.
Basically for us it seems to be that if it is warm enough inside the coach for human comfort, we have never worried about any of our water lines freezing.
I should add that our experience is based on our Monaco RV. Not all RV's are created equal and not all RV's may have the same insulation for the water lines or wet compartments. Only experience, trial and error, may tell you how your coach does in cold weather.