When installing gas lines in the crawl space of a house, what should you use when tapping into an existing gas line?

Using a ground joint union when tapping into an existing gas line is the appropriate choice because it provides a secure and reliable connection that can accommodate thermal expansion and contraction. Ground joint unions consist of two metal pieces that form a tight seal when joined together, which is essential for gas lines to prevent leaks.

This type of union is designed specifically for gas applications, as it is made to handle the pressures and specific conditions associated with gas distribution. The smooth connection and ability to be disassembled without damaging the piping make it very suitable for maintenance and repairs.

While junctions, all-threaded couplings, and unions are used in piping systems, they do not offer the same level of suitability and safety for gas lines as ground joint unions do. Junctions may not provide the same secure connection, all-threaded couplings can be cumbersome and difficult to seal properly in gas applications, and regular unions may lack the specific sealing capabilities required to ensure a leak-proof connection in gas lines. Therefore, the choice of a ground joint union ensures a compliant and safe installation when tapping into an existing gas line, making it the best option in this scenario.