I use 3.5 gallon buckets for drinking water for my ducks, it's big enough that they can dunk their entire heads, and heavy enough when filled that they don't knock it over, but small enough that they can't climb in and try to swim and slosh out all the water. (also a lot easier to carry than a larger bucket since I can't run the hose in winter and haul water from the house). I fill in the morning. I check and re-fill if needed in the afternoons. It is not heated. The ducks play in the water all the time and even when freezing they break the surface ice on the water. It takes an extremely cold day to freeze the water bucket all the way through. I generally keep another bucket in my house, so if the one in the run freezes I just swap it out with one that is thawed and ready to go. I have had heated waterers and have found they weren't always reliable in my situation. If I'm going out to check the water regularly anyway, it's not much harder to fill the water with fresh at the same time. Do not assume your water heater has kept things thawed if you choose to use one, definitely still check on your flock in bad weather.
