We set up aTT for extreme cold using old waterbed heaters on the underside of each tank and 5 watt/' cut to length heat cable on waterlines. They were thermostatic to set from 50-95 degrees F. Wintered over in Whitecourt Ab. at temps as low as -43f without freezing.
Cheap too!
They are 120v ac, so when traveling we ran them off the inverter when the truck was running, the genny or park power when parked. Forget 12v dc. You wouldnt get enough heat to do any good.
Wrap your dump valves, pump & outdoor shower, any suspect waterline while you are at it.