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

In plumbing regulations, particularly concerning gas systems, the use of cast iron is prohibited primarily due to safety concerns. Cast iron can be brittle and more susceptible to cracking under stress, which can potentially lead to gas leaks. Gas systems require materials that can withstand pressure and provide reliable sealing to ensure safety and prevent dangerous escapes of gas. Other materials like wrought iron, plastic, and steel, when used in compliance with the relevant regulations, can provide the necessary durability and resistance needed for gas systems.

Plastic, while regulated based on specific standards, is often allowed in certain gas application contexts under specific conditions, depending on local codes. Wrought iron and steel are also commonly used in gas piping, provided they meet the required specifications to ensure they are safe for gas transport. Hence, the prohibition of cast iron as a material for gas systems is rooted in ensuring the safety and reliability of these systems.