Hi, im new to nipple waterers I've always used bowls but latest additions were already onto these and I actually love it the water stays cleaner much lesss mess but my concern is how can I keep these from freezing in the winter? I use heated dog bowls for my older girls but won't work for these I use soda bottles not the bucket style waterers but if need to change for winter I could switch, I'm in Mass so can be very cold here in winter. Thanks for any ideas! Hate thinking of winter already but .......