We have a couple "Richie" automatic waterers, both with heaters for winter. Just connecting to a hot water heater is not going to keep your waterer from freezing. Also, be sure to have a back flow valve if your connecting to a water system that you or others may be using. There's some expense putting them in, burying water and power lines, but they are nice when they are working properly. If the waterer is inside a barn not subject to freezing, you may be fine, be sure, frozen pipes in winter are no fun.