What material should not be used for gas pipe fittings?

Plastic pipe should not be used for gas pipe fittings primarily due to safety concerns related to the integrity and durability of the material when exposed to natural gas or propane. Gas pipes are required to withstand high pressures and operate in various environmental conditions, including exposure to changes in temperature and pressure. Plastic does not have the same strength and heat resistance as metals, making it prone to deformation, cracks, or leaks over time.

In addition, plastics can degrade when exposed to certain chemicals that are often present in natural gas, possibly leading to failure in the piping system. As a result, for gas applications, materials such as steel, copper, and galvanized pipe, which are recognized for their strength and resistance to corrosion, are preferred and commonly accepted in plumbing codes and standards. This ensures a safer installation and minimizes the risk of gas leaks that could pose health hazards or lead to dangerous situations.