Well.. I go to South Carolina myself.. Just a short day out of TN (on my way south my last night "On the road" was spent in, I thinkm, Viola, TN. less than 200 miles from Seneca, SC 200 of which about 150 was Foothills driving,, (Not the easiest, nor the hardest, roads I have ever trod).
One option is to winterize (I like the dry method) the fresh system and carry water inside the heated RV.. of course this leaves your exposed pipes at risk if you have any but they can be protected.
A 100 watt light blub or two can put out a lot of heat.. Just make sure it is the old fashion kind, not the new fangled low-power ones Or a 150 watt Infra Red spot or flood. But be careful with those in enclosed spaces (DO NOT USE)
You can take a coffee can, a block of wood (or metal) a porelin lamp base, a large coffee can and some flat black paint.
Paint the can inside and out
Put 75-100 watt lamp in light fixture (Actually a porcelin ceiling/wall type fixture on a box nailed to a say six inches of 2x6 might work well or fill the base with plaster)
Makes a fairly good low wattage heater. (But I do not cover my light-bulb-heaters.. I let the light shine on what I want heated, Works better that way)