I will be moving my mother-in-law down from the tip of the thumb in Michigan for the winter. I need some help in this venture. The home is approximately 3000 sq.ft. ranch. It is built over a crawl space which has been properly insulated, batted and vented. She would like for me to keep the water on. At what temperature do I need to leave the furnace on to prohibit the pipes from freezing. Also if there any other suggestions I should know please feel free to mention. Thanks.