How to keep jerry cans from freezing when boondocking?

SteveAE, i really like that idea. Using the relatively small amount of water, recirculating back to the tank (or pump input) due to the pressure difference when the solenoid valve is opened is a great idea. The pressure tank allows more of the water to move before the pump turns on. Then, if the pressure never reaches the pump shutoff value, it just recirculates. A timer would be helpful here.
Nice mod.
Mike