Backflow-prevention devices are required by law in most areas. PVC is so common that all the underground pipe in your irrigation system will be PVC except for where you attach your system to an above-ground water meter. Plumbers use copper pipe to make this connection. PVC pipes have a flared end and a standard end. The flared end fits over the standard end when connecting the pipes with solvent.
Plumbers use more expensive, heavier gauge pipe where pressure is highest.
Other parts of the plumbing can withstand less expensive, thinner gauge pipe. Pipe fittings You can choose from a wide variety of pipe fittings to suit all your needs. Fittings can make your pipes turn corners, go up or down to avoid obstacles, or connect PVC to copper or galvanized pipe, for example. Fittings either screw together or need to be connected with PVC glue. Risers Risers are vertical pieces of pipe that connect underground pipe to the various sprinkler heads.