Hi all,
I came across this suggestion in a yahoo group and thought it quite innovative.
"Install Valve and fittings necessary to recirculate H2O from Water Heater to Fresh H2O Tank. Per NeonJohn: Here's what I've done to my MH for single digit camping. I installed a valve that lets me run hot water from the water heater back into my fresh water tank. I also installed an indoor/outdoor thermometer with the bulb hanging down into the fresh water tank. When I'm camping in sub-freezing temperatures, I watch the temperature of the water. When it reaches 32 degrees, I open the valve which sets up a recirc loop between the water heater, the water pump and the fresh water tank. I let it recirculate until the water heater has brought the fresh water tank up to 70 degrees or thereabouts. Even in the coldest weather that I've camped in, I've only had to do that a maximum of twice a day. More usually once a day. This is, of course, using propane to heat the water so you'll need a decent supply. My rig has an 80 lb frame-mounted tank so I'm good to go in that regard. I've been using this system for better than 10 years and have never had any freezing problems. This was probably my favorite suggestion – so logical and simplistic."