Thank's all for the input.
I will redesign my plans,tromb walls and rooms with rock floors in solar applications are the reason i asked.
The idea of heating water so other water doesn't freeze is kind of hard for me to understand especially to see an vehicle not retain heat in the cold after a few hours and it takes a while to re heat,although sitting in the cold an engine block V8 USA (STEEL)type filled with antifreeze. One would think steel filled with antifreeze,(yes non insulated) running hot doesn't retain heat that long.(if you think about it?)
My utilty room will be more than well insulated though,(MASS),i guess is what matters.
Thank's again for all the input!