Fuel Gas Piping and Appliance Connections
Materials and routing
Black steel pipe is the default. CSST is common in residential work and must be bonded. Copper is restricted and must be rated for gas service; PVC and other plastic are prohibited for gas piping inside the building. Pipe must be supported, protected from physical damage, kept out of ducts and plenums, and not concealed where joints are prohibited. A sediment trap (drip leg) at each appliance catches debris before the controls.
Sizing
Sizing uses BTU input, longest length from the meter, gas specific gravity, and allowable pressure drop. Use the longest-length method: find the total connected load and the distance to the farthest appliance, then read the table. Undersizing shows up as appliances that will not hold a flame when several are running at once.
Connections and testing
Each appliance gets a shutoff valve, a union or approved connector, and a sediment trap. Appliance connectors are limited in length (commonly 6 ft or less, shorter in some codes), cannot be concealed in walls or floors, cannot pass through cabinets or appliance housings, and cannot be reused. The system is tested with air or inert gas before the meter is set, with the gauge watched and no drop allowed.
Traps
- Skipping the sediment trap, or locating it where debris cannot fall out.
- Running a flexible connector through a wall or concealing it.
- Assuming any plastic pipe can carry gas.
- Forgetting bonding for CSST.
- Failing to cap and test every outlet before the inspection.
Rule of thumb
Longest run plus total BTU load decides pipe size. When two appliances share a line, the size is set by the farthest one, not the nearest.
Example: a 40 ft run from the meter serving a 60,000 BTU furnace and a 40,000 BTU range is sized for 100,000 BTU at 40 ft.