I found a nice, easy (and fairly inexpensive) way to keep the waterer from freezing. I bought a single 8' x 8' cinder block, put a 25 watt light bulb inside it and set the waterer on top of the cinder block. I then found a temperature controlled plug that turns on at around 35 degrees and off again when it goes up to about 40 degrees. It works like a charm and I never have to worry about frozen water.