Plastic pipe in a coil
Steel pipe
Distribution pipe installed today may be steel or plastic. Typical pipe thickness is 1/8 inch to 1/4 inch for steel, and 1/2 inch or heavier for plastic. 1 1/4- to 6-inch diameter gas distribution mains are typically installed in every street or in back property alley lines in older residential areas. In a residential area, service lines that are 1/2 inch or 3/4 inch diameter extend from mains in the streets to each house. Larger diameter service lines are used for larger customers including businesses and industrial facilities.
The steel pipe that is used in distribution systems can be significantly lower in strength than transmission pipe since the lower operating pressures result in relatively low-stress levels. Sections of pipe are connected by welding in the field. Minimum wall thickness in distribution pipe is generally determined not by pressure stress but by other criteria such as resistance to third-party damage and ease of field welding. These concerns typically require pipe thickness of greater than 1/8 inch even if this is not required due to pressure stress.
Plastic pipe is commonly used as a more economical choice than steel pipe for sizes 6 inches and down. Sections of plastic pipe are connected by heat fusion, electro-fusion, or mechanical coupling. Three-inch and smaller diameters are available in rolls, which allows for fewer joints and lower-cost installation. Plastic pipe also has the advantages of flexibility for installing around corners, corrosion resistance, and low installation costs. However, it is more susceptible to damage than steel pipe.
In early times, cast iron pipe was used for distribution, and these pipes still exist in some areas. But they are prone to leaking and are commonly scheduled to be replaced as quickly as is feasible.