On a natural gas metallic piping system, the unthreaded portion of piping outlets shall extend not less than how many inch(es) through a finished wall?

In a natural gas metallic piping system, the requirement for the unthreaded portion of piping outlets to extend through a finished wall is established to ensure proper installation and safety standards are met. The correct answer is that this portion should extend not less than 1 inch through the finished wall.

This specification is in place to minimize the risks associated with gas leaks and to provide sufficient access for connections to appliances or equipment on the outside of the wall. By ensuring that the piping outlet extends at least 1 inch, it helps to prevent any potential encasement of the piping due to wall finishes or other coverings that may inadvertently obstruct or damage the pipe, which can have serious safety implications in a natural gas system.

Options that specify a greater extension, such as 2, 3, or 4 inches, may not correspond with the codes that aim for a balance of accessibility, protection, and practical installation. The standards are designed to provide necessary clearance while not requiring excessive piping length that could complicate installations or maintenance. Thus, the established requirement of 1 inch meets the safety and operational standards for effective gas piping installation.