Here in Minnesota i have a kiddie pool spring, summer and fall until it freezes over and I am sick of breaking ice daily. I then move a sheep tank into the barn and cover it with a piece of plywood until that too freezes, then put a tank heater in it. I doubt the plastic kiddie pools could handle a heater unless you rigged it so the heater touches nothing.
I keep wood over the sheep tank because the chickens might fall in!
I give the ducks supervised swim time while i do chores and I pull out the heater and unplug it while they swim, several times a week. They love it, but around feb. they usually lose interest in the tank. I'm guessing the 'warm' water is great until they have to get out in the cold again.
If you can't get a sheep tank or such, a tub that you could easily empty out might be the way to go since it is nice to have enough water to splash on themselves for grooming, although I am sure there are many ducks who cannot bathe during winter.
I know water for swimming in the frozen winter is a total pain. Anything you splash out seems to freeze. I have a sump pump i put in the sheep tank to clean it out, then drag it out to dump the last bit and rinse outside. Let's just say the tank doesn't get emptied as often as it should.
I do use plug in water bowls and yes they freeze to the ground. I just kick them loose (which makes them splash which makes them freeze to the ground again!!) to clean them.
Up here
Walmart has large ones for $20. I've found smaller ones for the same price at other places.
I've also had to put a heat lamp over the heated water bowls when the temps really drop, or they freeze over just enough to prevent birds from drinking!!!
