I have 13 water bowls from very old to new, and from 4 different makes. None of them are fool proof when you get very cold winters like we are having right now. Six years ago, I started putting in- line heat tapes in the water bowls and since installing them, I have not had any problems with water bowls freezing. These heat tapes go right into the water line and come out just below the bowl and so far they have saved me hours and hours of kneeling beside a water bowl trying to thaw it out. I am not sure if these heat tapes are custom made by a company or not, but a local feed store owner has them made for him locally. He sells hundreds of them every year.
The only issue I have had since installing these in line tapes happened last winter when one water bowl quit working. It turned out that the water line froze on the way to the fountain despite being buried 8 feet in the ground. We had very little snow, and the frost kept going deeper in the ground in the cold weather. All I could do was wait for spring to arrive and it finally thawed on June 23rd. So far this winter, no problems at all.