Here in the desert, during the winter we get freezing down to 1 foot acording to our building dept. Ever since last spring, I have been adding more zones and replaced some pipe in the original zones that were exposed to sun. Never before have any of these original systems froze, so for my additional pipes I made sure to make them slightly lower then the originals. Now it is time to backfill all the trenches. But I wanted to backfill with compost however, my brother tells me that I might have freezing problems if I do that.... My brother is well known for teezing me and giving me a hard time, so Im not sure if this is true or not... IF it is true, then what would you pro's suggest to protect my pipes? I had 2/3s of the original dirt hauled off already...