This is my first time having chickens. Where I libe the temperature can go to -30 and sometimes -40 degrees C over night. Most night aren't that cold but we sometimes have winters that are -20 for weeks. I have 5 chickens. What is the best heated waterer that I could make or buy. I am usually always home but one week in the winter I like to go away for a week somewhere warm so I would like a large enough reservoir so who ever checks in on my chickens doesn't have to fill water daily. Also, I will not be putting any heat lamp in the coop. Any ideas? Thanks