Piping, tubing, fittings and gas supply systems
Materials and joints
- Use black steel or wrought-iron pipe for above-ground gas piping unless the code permits another listed material. Copper tubing may be permitted for natural gas and propane in specific applications; verify the code and manufacturer limits, particularly for propane and buried lines. CSST must be listed and installed with its manufacturer's bonding and routing rules.
- Threaded joints use approved pipe dope or tape on the male threads, leaving the first one or two threads clean. Flared fittings are made with a proper flaring tool; do not use compression fittings where the code prohibits them.
- Support pipe at code intervals, protect it from corrosion and physical damage, and bond CSST and metallic piping as required by CSA C22.1 and the manufacturer. Never use gas piping as an electrical ground.
Sizing, pressure and regulators
- Size by the longest-run method: total connected input, allowable pressure drop, equivalent length of fittings and gas specific gravity. Use the code tables.
- Low-pressure natural gas is typically supplied at 7 in w.c. with a 0.5 in w.c. allowable drop; propane at 11 in w.c. Higher supply pressures need a regulator at the appliance.
- Regulator vents must be protected from blockage and, where required, vented outdoors to a safe location. Install a sediment trap at the appliance and a manual valve ahead of it.
- Appliance connectors are limited in length (commonly 6 ft), must be accessible, and must not pass through walls, floors or ceilings.
Testing and purging
- Pressure-test new or altered piping with air or nitrogen, with appliance valves isolated, at the code test pressure and for the required duration. Never use gas or a flame for leak testing.
- Purge only as part of a controlled start-up; discharge purged gas to a safe outdoor location and never into a confined space.
Worked example: a capacity table is based on 0.60 specific gravity. A 1 in pipe is listed at 200,000 Btu/h for the run. For propane at 1.52 specific gravity, the capacity is 200,000 × √(0.60/1.52) = 200,000 × 0.628 = 125,600 Btu/h. The same pipe carries less propane because the denser gas flows less readily; do not size propane from a natural-gas table without correction.
Traps: using nominal pipe size as inside diameter; ignoring equivalent length of elbows; pressure-testing with gas; leaving the appliance connected during a high-pressure test; blocking a regulator vent; routing an appliance connector through a cabinet wall.