I have 2 550 gallon poly water tanks in the crawl space under my house. They are 42 inches high and about 6 feet in diameter. I have them partially buried so just the tops are exposed to air. The crawl space is well insulated.

I will only be visiting the house in the summers and it will be mostly vacant and unheated in the winter. I am unsure if they will freeze, but I am leaning more towards them NOT freezing.

The house is in Wisconsin. What do you think?