What material is typically used for gas piping in residential plumbing?

Black iron and flexible CSST (Corrugated Stainless Steel Tubing) are the standard materials used for gas piping in residential plumbing due to their durability and resistance to corrosion. Black iron has been traditionally used because it can withstand high pressure and temperature, making it suitable for natural gas and propane installations. Flexible CSST offers the advantage of ease of installation and adaptability in tight spaces, which can reduce the number of fittings required and minimize potential leak points.

Copper and PVC, while useful in other types of plumbing, are not appropriate for gas piping. Copper can corrode when used with gas, and PVC is unsuitable due to its inability to withstand the pressures associated with gas systems and its susceptibility to damage from UV light and extreme temperatures. Galvanized steel can be used in some applications, but it is not as common for gas piping as black iron and flexible CSST.