if your hydrants are freezing they are either not draining or not buried deep enough.
these are best brands, from my experience:
Woodford
Merrill
Campbell
great tip re: disassembly/re-assembly before installation, turnkey
i did a few this past summer. some of my "rules":
1. always put an elbow on the subgrade drain outlet to help keep it clear
2. stainless oetiker clamps and brass fittings if attaching to poly (no plastic barbs or worm clamps)
3. lots of crush wrapped in geotextile fabric
4. name-brand hydrants with local replacement/rebuild parts availability (list above)
5. drain/waste stop valves placed as necessary to isolate legs in case of repair/failure
i special-ordered
THIS woodford for installation in my barn. it wasn't cheap but the build quality is amazing, it was made-to-order, and arrived at my plumbing supply in just a week's time. would definitely buy from them again.