We are piping an outdoor shower. The water supply from the house will be under concrete and the pipes (PEX) themselves will be 12" in the dirt below the concrete. Where the pipes stub up from underground, we will use pipe wrap. Can we just run the PEX in the dirt (there are no unions or connections)? Alternatively, do I have to sleeve the PEX in a PVC pipe where it is underground? There is NO freeze problem here in Southern CA. Just askin'