How much unthreaded pipe must extend beyond the finished wall or ceiling when penetrating a structure?

The correct answer is that unthreaded pipe must extend at least 1 inch beyond the finished wall or ceiling when penetrating a structure. This requirement is in place to ensure adequate clearance for connection fittings and to prevent any potential leaks in the gas line that could occur if the pipe were to be flush against the wall or ceiling. Extending the pipe beyond the finished surface also facilitates easier maintenance and replacement of components, providing access for proper servicing and adjustments if needed.

This 1-inch extension helps to prevent any interference from drywall or other materials that could obstruct the connection to appliances or other piping systems. It is important for safety standards and efficient operation, making it a critical consideration in gas installation practices. Other lengths, such as 2 inches, 3 inches, or 4 inches, would provide unnecessary additional length, complicating installation without any added benefit while also potentially introducing risks if the pipe extends too far beyond the structure.