Fuel Gas Piping and Gas-Fired Appliances
Pipe, sizing, and joints
- The District adopts the International Fuel Gas Code with amendments; the gas chapter governs materials, sizing, installation, and testing.
- Acceptable materials include black steel pipe, corrugated stainless steel tubing (CSST), and copper where the code permits it. PVC and other unlisted plastics are prohibited.
- Sizing uses the longest-length method: convert appliance input from Btu/h to cubic feet per hour (natural gas is roughly 1,000 Btu per cubic foot), then read the table for the longest run at the permitted pressure drop, about 0.5 in water column for low-pressure systems.
- CSST must be bonded to the electrical grounding system per the manufacturer's instructions.
- Piping through walls needs protection or a sleeve; piping may not run through ducts, plenums, or chimneys.
Appliances
A shutoff valve is required upstream of each appliance, plus a sediment trap at the inlet. Flexible appliance connectors are limited to about 6 ft and may not pass through walls, floors, or ceilings. Venting and combustion air follow the appliance category: a Category I appliance vents into a listed vent with proper clearance to combustibles, while a direct-vent appliance takes air and vents per its listing.
Worked example
A range rated 35,000 Btu/h, a water heater at 40,000, and a furnace at 80,000 total 155,000 Btu/h. Divide by 1,000 for about 155 cubic feet per hour. Measure the longest run from the meter to the farthest appliance, then size that entire run for 155 cfh - not each branch for its own appliance. Branch lines downstream are sized for the load they individually carry.
Traps that cost marks
Sizing each branch independently and under-sizing the main; checking for leaks with a flame instead of soap solution or an electronic detector; omitting the sediment trap; running a connector beyond 6 ft; and pressure-testing at the wrong level, since the test is typically 1.5 times working pressure for the hold period stated in the code.