The National Electric Code requires that wire placed in Schedule 80 PVC must be buried at least 18 inches below ground. If the wire is being buried without PVC, it must be at least 24 inches underground.
Schedule 80 PVC, or conduit, is a gray pipe that looks similar to white- or cream-colored water line. This conduit is often used in buried wire applications as it provides an extra layer of protection to the wires. PVC conduit is often chosen over metal conduit for its cost effectiveness and its resistance to water and corrosion. The National Electric Code recommends calling local utility companies before digging to be sure of the placement of any dangerous underground lines or obstacles.