I'm having a hoop barn built next week. This will be an unheated barn. I'm having a hydrant put inside for water. I have 2 other hydrants on the farm, one outside, one inside another barn. The outside one always freezes in cold weather, the inside one usually doesn't until temps go below zero. These are placed at least 5 feet deep, and the vertical pipe is sheated by a 6" pvc pipe filled w/ gravel. What is the best technique to set the new one up and prevent freezing?