Gas Piping and Fuel Gas Systems
Materials, routing, protection
Gas piping follows the fuel-gas chapter of the adopted plumbing or mechanical code. Use listed pipe and fittings: black steel, corrugated stainless steel tubing (CSST), or approved plastic where allowed. Protect pipe from physical damage and corrosion, sleeve it through masonry and concrete, and keep it out of air ducts, plenums, and elevator shafts. CSST must be bonded to the grounding electrode system per the manufacturer instructions.
Appliance connections
- A shutoff valve is required at each appliance, upstream and within reach.
- A sediment trap, or drip leg, is required at the appliance connection so dirt falls into the leg instead of the controls.
- A union or approved connector is required for appliance removal; flexible connectors may not pass through walls, floors, or ceilings.
- Appliances need combustion air and listed venting; a Category I appliance uses a vertical flue, a power-vented unit uses its listed vent material.
- Piping is pressure tested before the meter is turned on, with the gauge left in place for the inspector.
Sizing example
Connected load: range 65,000 Btu/hr, water heater 40,000, furnace 100,000, dryer 35,000, totaling 240,000 Btu/hr. The longest run from the meter to the farthest appliance is 60 feet. Enter the sizing table at 60 feet and 240,000 Btu/hr for the main size, then size each branch at its own longest length and its own load. Undersizing the main is the classic failure: the farthest appliance starves.
Traps that cost marks
Omitting the drip leg, using a valve as a union, failing to bond CSST, and sizing on the nearest appliance instead of the longest run.