It is a fact that North Carolina is located in a part of the U.S. where the frost level can extend below the depth of installed pipe. Why is this important? Because the PVC pipe (the white pipe installed underground) can suffer significant damage from expansion and contraction. If the pipe is more than half full of water and temperatures are freezing, this water will freeze and cause the pipe to expand. This will result in the PVC pipe cracking (usually along the length of the pipe from fitting to fitting). Repeated water expansion inside pipes can weaken the pipes and cause fractures and even breaks in the piping. It is necessary to winterize your irrigation system every year! These repairs can be very expensive and they are not covered under warranty if the system is not winterized by Overstream.