Which material is prohibited for use on gas systems according to plumbing regulations?

In the context of plumbing regulations concerning gas systems, the use of cast iron is prohibited due to safety concerns. Cast iron, while strong and durable for many applications, is not suitable for gas lines primarily because it is prone to cracking under stress, especially in situations where temperature fluctuations or ground movement occur. This cracking can lead to gas leaks, which can be dangerous.

Plumbing codes emphasize the importance of using materials that ensure safety and integrity within gas distribution systems. Other materials, such as wrought iron, plastic, and steel, have specific applications where they can be safely utilized. For instance, plastics designed for gas service are tested for durability and resistance to corrosion, while steel pipe is robust and resistant to the types of stresses that might otherwise lead to failure in a cast iron infrastructure. Thus, the choice to prohibit cast iron is a key safety measure to prevent possible gas leaks and ensure the reliability of gas installations.