Hi,
The OP said "forced to stop" That to me implies no shore power. With exposed tanks, likely the thermal mass will keep them from freezing. The supply lines are a different matter.
If the OP has an air compressor, he could by pass the water heater and blow out the lines.
Run the furnace, and keep the water heater on.
The big issue may be the dump valves. If there is a generator then using a 120 volt heating pad may be used. If not, then a 12 volt heating blanket could be used. Be aware that the 12 volt blankets often have a timer built in to prevent them from draining the battery bank--which means that about every three hours they shut off.
