This is a fun thread to read and think about all the ways to skin the "watering in a cold climate" cat. I will show yet one more solution, but there are very few people it will work for. We have artesian springs on the farm (hence the name). At least 100 years ago, the dairy farmers here before my grandfather put a hunk of culvert where one of those springs is and then started running line from there. We now have over 3/4 mile of pipe run all over the farm from this little dug well fed by a spring. There's never more than 30 gallons in that well but its always flowing at full pressure (I think about 20 PSI) even at the end coming out of a 3/4" pipe. We have slowly perfected a system in rubbermaid tanks that allows us to run pretty much as many waterers as we want. They all look something like this:
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This was a below zero day, of which we get plenty in an average winter. With all our fittings inside and this vertical outlet to create a swirl at the top, we have enough disturbance, even with quite low flow, that nothing ices over any more than what you see in this picture. Even as I explain I'm reminded of how much we take this water for granted!