In your environment, depending on the type of waterer, I'm assuming you're referring to freeze proofs, it can get to be sort of complicated. For some types they rely on a deep hole under the waterer to provide earth warmed water to prevent freezing, other wypes have a continuous trickle of water. Those that have water running hrough them to prevent freezing requires a pretty good drainage system to keep from having ice problems either in the overflow line or in an area that the animlas can access and slip and fall. We have several different tye of Ritchie waterers, but I really like the Nelson types, mainly because they're easy to clean and they're stainless. The Nelsons require a deep hole, the Ritchies use running water or a ball to protect the water. Even with the ball properly adjusted I've had the water in the reservoir freeze solid. Most companys address the capacity by the number of head to be waterered. I'm sure that works for some, but all of ours tend to wander up for water pretty much at the same time several times a day. That leaves long periods of time for the cold to do it's nasty work.
dun