I did this my first year with my first chickens... It worked keeping the water from freezing, but it was HELLA HOT! And going back to my original statement of heat being bad for chickens that are in and out.... I didn't do it again. I just have two waterers for every coop. In the winter I change them out. I have a full basement that makes this possible. Bring frozen in, allow them to thaw, then change them out. Not ideal, but it was we did over time. Someone told me once they put salt in their water, but I do not recommend trying that. I don't know how safe it is, but they do it.