From the 2015 International Fuel Gas Code (IFGC)
- Cast iron: Not ALLOWED
- Steel: Black iron or galvanized. Schedule 40 minimum.
- ASTM B36.10 or 10M
- ASTM A53/A53M
- Copper or copper alloy: Check with the local Gas Utility. Permissible use varies with hydrogen sulfide (H2S) content of gas. Excessive levels of H2S reacts chemically with copper to produce particles that can become lodged in the gas valve if no sediment trap is installed. Most natural gas is OK.
- Aluminum-alloy: Seldom used due to highly reactive characteristics.
- ASTM B241 (must be marked at both pipe ends indicating compliance).
- Alloy 5456 prohibited
- Steel tubing: Typically used only in industrial applications and for appliances
- ASTM A254
- Copper tubing or copper-alloy tubing:
- ASTM B280
- Standard types K and L, not M.
- Aluminum tubing:
- ASTM B210 or B241
- Must have a protective coating applied where it contacts masonry, plaster, or insulation, where it may be repeatedly wetted by water, detergent, or sewage.
- May not be used underground or at exterior locations.
Plastic tubing is allowed outside and underground only.
- Polyethylene (PE)
- Must be marked “GAS” and “ASTM 2513”
- PEX: PEX is short for “cross-linked polyethylene”. It’s simply polyethylene with polymers added to enhance certain characteristics. Requirements are the same as for polyethylene.
- ASTM F2785 (may be different in the past)
- Polyvinyl Chloride (PVC): NOT ALLOWED
- Chlorinated Polyvinyl Chloride (PVC): NOT ALLOWED
Difference Between Pipe and Tube
- Pipe is measured by outside diameter
- Tube is measured by inside diameter
- Wall thickness
- Pipe is described by “schedule thickness” (schedule 20, 40, etc.)
- Tube is described by “gauge” for thinner tube, and by fractions of an inch or millimeter for thicker tubing.
- Cross-sectional shape:
- Pipe is always round
- Tube may be round or square.
- Manufacturing tolerances
- Tube is typically manufactured to closer tolerances than pipe