When installing gas piping, which type of fittings is specifically prohibited upstream of the service regulator?

When installing gas piping, compression fittings are specifically prohibited upstream of the service regulator because they can pose safety risks in gas applications. Compression fittings rely on a mechanical connection that can potentially become loose over time due to vibration, thermal expansion, or changes in pressure. If a compression fitting were to fail, it could lead to gas leaks, which would be highly dangerous given the flammable nature of gas.

In contrast, other types of fittings, like flared fittings, solder fittings, and threaded fittings, have been proven to provide secure and reliable connections in gas piping systems. Flared fittings create a strong seal through a conical shape and are generally safer in high-pressure situations. Solder fittings, while more commonly used in plumbing for water rather than gas, can be reliable when used correctly with appropriate materials. Threaded fittings are widely accepted for gas applications when properly installed with the correct thread sealants to ensure a leak-tight joint. Thus, understanding the limitations and appropriate applications of each type of fitting is crucial for ensuring safety in gas installations.