If it is just parked, and it is there all winter in makes it a lot easier. Personally, I would not leave the grey tank valve open, while there. The cold air will enter the tank any water condensation will freeze and make a mess.
Personally, I would build a simple skirt around the trailer, ideally with some high density foam and then some type of cover, plywood or aluminum soffit type material. This will keep a lot of the cold out, so you can heat the area as a bonus the floors will feel warmer. With a skirt a couple 100 watt light bulbs will keep the underside from freezing.
Also if it just has a simple underbelly that is not insulated, I was also consider the heated tank pads.
Hey Mike, those adapters don't work? Even if you freeze the tank first? Looking at the You Tube videos it sounds like that's the key. Yes, they probably don't fill 100% but even 80% would be cost effective. The trouble with just using a hose from a 20 pound take is where will I store that tank? This hot water heater and the 7 gallon water jug I'm going to use for the water supply will take up enough from in my small bathroom.
If the propane connection on the shower will only accept the small 1# propane bottles, just get a hose that will fit the shower propane connection and a 20# tank, problem solved. I got a hose with these connections for a Weber Q and works just fine.
Of course! My tanks are in the front and my camper hot water heater is in the rear. Of course I can tap off that. What was I thinking?
It looks like I have a mod in my future..
Thanks guys for the tips.