I currently water my flock of 13 chickens with a metal waterer. In the winter (I live in New Hampshire, so it gets mighty cold), I set it atop a heating element designed for waterer. It works great at keeping the water thawed out, since the coop is not heated. However, I dislike the metal waterers because I don't take care for them the way I should, and they rust rather quickly. The platic waterers look appealing, but how do I keep the water thawed in winter if I switch to plastic? I believe the the heater element is designed for metal waterers only. Any suggestions??? Or am I doomed to stick with metal?