[Dexter]

What I do is discommect the water hose and drain it. Close the hatch and make sure the furnace runs at least part time because the water lines and tanks are heated areas by the furnace. us the water pump until it warms up.
It got down to 7 degrees here last night and looking for the same tonight. no problem. The water from the taps even warmed up enough tu fell the dif.