Keeping the water from Freezing

We have learned when we are at home that we need to keep the sleeper from freezing. It is pretty amazing how fast the temperature in our sleeper can drop below the freezing point. Bob spreads out an extension cord to a space heater in the truck from the shop. He then lifts up the bed and also opens the cupboard that has our water pump stored. We also fill our water tank as full as possible when we get home. The little space heater will just keep the sleeper above freezing and keeps everything in good working order. When on the road we do not have this problem as we keep the generator set at 65 and the sleeper stays pretty warm.