Since like me, you're retired and also you're present at the end of the day for coop lockup, have you considered just taking the waterers into the kitchen at night? Either let them thaw out/ warm up overnight, or take the opportunity to wash them or swap them out for clean jars.
I also read recommendations to not keep water in the coop due to needing to minimize humidity, especially in the cold for frostbite prevention. I have a Nestera coop, and about all that will fit inside are the actual chickens, lol, and have a wall-mounted waterer out in the run. But I'm taking it in at night as well.
Chickens are eating and drinking at night, so other than the nuisance of toting things back and forth, it's a pretty handy solution. And low-tech!