Preventing freezing pipes during the shoulder season

As stated above, the propane furnaces used in RV's are very inefficient. Plus, the forward furnace in our rig supply's heat to our water bay BUT is piped on the opposite side of the actual valves and such. Cant get enough heat to prevent from freezing thus the need for electric heater in the water bay.
Will use unvented propane heat during the day with proper venting but won't use at night while sleeping.