PEX placed in soil consisting of rock shall be covered with ______ inches of coarse sand or pea gravel.

The correct answer is based on the requirement for protecting PEX piping when it is laid in soil that may contain rocks. When PEX is installed in such conditions, it is essential to cover the piping with a protective layer to prevent damage from sharp edges of rocks or other abrasive materials. The code typically stipulates that at least 6 inches of coarse sand or pea gravel should be used for this purpose. This ensures that the PEX is adequately cushioned and shielded, reducing the risk of punctures, kinks, or other mechanical stress that could lead to leaks or failure of the piping system over time.

Using 6 inches of coarse sand or pea gravel strikes a balance between providing sufficient coverage while adhering to safety and building code guidelines, thus ensuring the longevity and integrity of the piping system.