Stay away from the ball type drinkers they are like toilets, very nasty plus we have freezing issues with them, cattle drip water on the ball when drinking and then they freeze up, esp over night, hubby is constantly carrying hot water out to them when in gets below 20 to unfreeze the ball. they are then fine all day but overnight ill freeze up again., you can manipulate water levels but I would avoid the aggravation and go with something other than a ball type.
We use both the water master, no heat to keep from freezing it, just a constant water trickle plus enough cows
even in the neg numbers no problem, and the omni fount we have out in the open on an 80 acre pasture, but it is heated, We are going to replace all our ball type mirafounts one of these days really hate them! As I said they are just nasty!
Here is their website
http://www.ritchiefount.com/products.html