Originally Posted by garyoregon
Is it an automatic check valve, or do I need to flip a switch? Thanks for your patience with this "junior member"
The check valve is built into the onboard pump. If it malfunctions you will fill your tank with city water and water will come out of the overflow once the tank is filled. This rarely happens, but it can.
If it is not too far below freezing you'll be fine with your hose hooked up overnight. If it is getting really cold I would unhook the hose. If it is really cold and you want to maintain water service you would need an insulated, heated water hose. This is only practical with full hook-ups as you would need electric for hose heater and would keep your gray valve open for any waste water to go right thru the tank and into the sewer system.
Another way to handle it is to work with a container of water within the trailer as your supply. Still have to deal with the gray water though.