What is the code for the minimum depth for direct burial of non-metallic conduit?

The minimum depth for direct burial of non-metallic conduit is 18 inches, as specified in the National Electrical Code (NEC). This depth is established to ensure sufficient protection for the conduit from physical damage and to minimize the potential for interference with other underground utilities or structures.

When non-metallic conduit is buried at this depth, it helps to adequately shield it from environmental factors that could compromise the integrity of the conduit, such as soil movement, frost heave, or other external forces. This standard is critical to maintaining the safety and reliability of electrical installations.

The other depth options exceed the NEC requirements for non-metallic conduits. For typical installations, going deeper than 18 inches might not only be unnecessary but could also complicate the installation process without providing added benefits in terms of protection. Thus, adhering to the 18-inch standard is both practical and efficient.