Hint: most furnaces are close to the water-pane & pump area. Expand a furnace duct to this are with a damper installed so you can shut off or regulate the heat to this area.
Frost always comes as a surprise (weatherman usual thinks ahead and is mostly wrong - as an RVer you constantly have to stay ahead of the game)
A couple of years ago in AB-Canada we had an early September freeze, had to replace a few toilet valves and filter-housings.
2014 Ram 1500 CrewCab 4x4 5.7 Hemi 3.92 Rear and Air Lift 1000
2005 Jayco Jay Feather LGT - 29Y GVWR-7000 lbs.
Dexter Axle Lift 4-9/16" - installed with sub-frame.
Pro Series 1200 lbs. WDH with Double Sway Bar.
Champion 3100/2800 watt Inverter/Generator-Onboard Solar Power