Connecting the Pipes
Eighty percent of the pipes used in residential in-ground irrigation supply are made out of PVC. Polyethylene or polybutylene plastic pipe (poly pipes) is also used because it's easier to work with, less expensive, and less likely to crack during a winter freeze. PVC is a rigid plastic and is the strongest of the three; it should always be used at the main water supply to the sprinkler system.
PVC water lines are laid out in straight lines with 90- or 45-degree joints and in yards that are relatively flat. In hilly areas, or where a lot of twists or turns in the supply line are necessary, poly supply pipes are often used. Poly piping is easily curved using fewer fittings than PVC. Poly pipes are held in place with metal clamps.
A properly installed sprinkler line should last years without developing a leak. But human activity and earth movement can cause joints to fail and pipes to be cut or punctured. The first indication of a leak is low pressure somewhere in the irrigation system. Another good indication is a flooded yard.