When building or remodeling your home, you may need to deal with natural gas lines. In many parts of the country, regulations require that natural gas be carried by black pipe. These regulations have been modified in some places, but the underlying reason for the restriction makes clear where modifications are permitted.
In many areas of the country, black pipe is required for natural gas lines because of the way it is made. This kind of pipe is created as a long, continuous tube. JM Eagle indicates that this kind of pipe is also preferred because it is "lightweight, non-corrosive, available in coil lengths, and easy to install by heat fusion or mechanical fittings."
Other kinds of pipe were traditionally created by first making a long sheet of metal. This sheet is then bent lengthwise and welded up the long seam to create a tube. These types of producing pipe are described more fully in chapter three of Kawasaki Steel's book "An Introduction to Iron and Steel Processing." These pipes may have a greater chance of failure along the welded seam and in their less flexible composition than black pipe.
With new materials on the market and new technologies being developed for transporting dangerous substances such as natural gas, some areas have rewritten the regulations to allow for alternative delivery systems. Copper pipe, polybutelene and polyethelene are now also approved in specific applications in some areas. Always check your local regulations before installing new pipe.