Table 1 identifies the different types of copper tube allowable for use in fuel gas distribution systems in the U.S.A., along with the identification and availability of each type. Types K and L copper tube (ASTM B 88) and ACR tube (ASTM B 280), up to and including 1-inch outside diameter, have been used in fuel gas systems for many years. Usually, Type L is used for interior distribution systems and Type K for any underground lines. Though not commonly used in the U.S.A., seamless copper tube Type GAS (ASTM B 837) is commonly used and required in Canada for gas distribution systems.
The dimensions of copper tube used for gas installations are shown in Table 2. Tube and fittings in fuel gas systems are usually identified by their outside diameter (O.D.) rather than their nominal sizes. Designers and installers should be specific with size designations in their references and when ordering.
Copper and copper alloy tube (except tin-lined copper tube) should not be used if the gas contains more than an average of 0.3 grains of hydrogen sulfide per 100 standard cubic feet (scf) of gas (0.7 mg/100 L).