As long as you keep your furnace on (we set ours at 55 degrees when it is forecast to be freezing) and you have a heated underbelly you can use the water in your rig. We however, fill our fresh water tank and use the pump. Full timers deal with this stuff all the time. Heat pumps work great if the temp is above 40 degrees but when you are more comfortable with your systems, experiment and you will find how low your can use your heat pumps. Our bedroom one will routinely work down to freezing but our main one only works down to around 40 degrees. You may not have damaged anything at all if you did not have sustained freezing temps. When it is too low for our heat pumps, we put the furnace on 55 degrees and use a spac e heater. Closing off the rest of the TV from the sleeping area and using a space heater is freezing temps keeps us nice an warm overnight. Then we kick up the furnace in the mornin g to warm the rest of the rig up.
