2021 IFGC Chapter 4
Fuel gas piping is where a small mistake becomes a fire, so the 2021 IFGC gives it a full chapter. Chapter 4 runs from the point of delivery to the connection at each appliance. This lesson covers materials, installation, valves, sediment traps and appliance connections; sizing and testing come in Lesson 13. Texas cities choose their own codes, and Houston enforces the Uniform Mechanical Code rather than the IMC (Lesson 1), so check which code governs gas piping locally before you write a correction.
The chapter covers piping from the point of delivery to the appliance connections (401.1). When an appliance is added, the existing piping is checked for capacity and enlarged or supplemented if it falls short (401.4). Exposed piping other than steel and CSST carries a yellow label reading "Gas" in black letters at intervals of 5 feet or less, except in the same room as the appliance it serves (401.5). Meters serving separate consumers are not interconnected on the outlet side, and each meter's piping is marked (401.6, 401.7).
Cast iron pipe is not allowed. Steel, stainless steel and wrought iron pipe must be no lighter than Schedule 10 and meet ASTM A53, A106 or A312 (403.3.2). Copper pipe is barred where the gas carries more than 0.3 grains of hydrogen sulfide per 100 standard cubic feet (403.3.3). CSST must be listed to ANSI LC 1/CSA 6.26 (403.4.5). Polyethylene gas pipe must meet ASTM D2513 and be marked "Gas", and PVC and CPVC may never carry fuel gas (403.5). Pipe and fittings must be free of burrs and defects, and defective pieces are replaced, not repaired (403.6). Used pipe is reused only if clean and adequate for the service (403.2).
Schedule 40 and heavier pipe may be threaded, flanged, brazed, welded or joined with listed press-connect fittings. Pipe lighter than Schedule 40 is connected only by press-connect fittings, flanges, brazing or welding (403.9.1). Brazing alloys melt above 1,000°F and hold no more than 0.05 percent phosphorus (403.9.1, 403.9.2). Field threading follows Table 403.8.2: 1/2 and 3/4 inch pipe get about 3/4 inch of thread and 10 threads, 1 inch gets 7/8 inch and 10 threads, and 1 1/4 inch gets 1 inch and 11 threads. Thread sealant must be nonhardening and resistant to the gas (403.8.3).
Gas piping may not run in or through a supply, return or exhaust duct, clothes chute, chimney or gas vent, dumbwaiter or elevator shaft (404.3). Concealed piping stays out of solid partitions and solid walls unless it is in a chase or casing (404.4). Concealed fittings are limited to threaded elbows, tees, couplings, plugs and caps, brazed and welded fittings, and fittings listed for CSST or press-connect use (404.5). Piping may not pass through a foundation wall below grade; it enters and leaves above grade with the annular space sealed (404.6). Where piping in a light-frame wall, floor or ceiling is less than 1 1/2 inches from the face that will receive the finish, No. 16 gage (0.0575 inch) steel shield plates cover it, extending 4 inches beyond each side of a framing member it crosses; black and galvanized steel pipe need no plate (404.7). Piping in a solid floor lies in a channel that can be opened with little damage, or in Schedule 40 conduit (404.8).
Outdoor piping stands at least 3 1/2 inches above the ground or roof surface and is supported and protected (404.9). Underground piping is buried at least 12 inches, or 8 inches for an individual line to an outdoor light or grill where approved (404.12), and zinc coating alone is not adequate protection (404.11.1). Beneath a building it must be encased in a conduit, which is sealed at the building end where the conduit starts outdoors (404.14). Plastic pipe is used only outdoors underground, never within or under a building or slab, at no more than 100 psig for natural gas; listed risers and outdoor patio, walkway and driveway slabs are the exceptions (404.17.1). Outlets not serving an appliance are capped gastight, and an outlet's unthreaded end extends at least 1 inch through a finished wall and 2 inches above a floor (404.15, 404.16).
CSST is installed to its listing and the manufacturer's instructions (404.2). Other above-ground gas piping likely to become energized is bonded through the grounded appliance it serves (310.1). CSST without an arc-resistant jacket is bonded to the service grounding electrode system with a jumper not smaller than 6 AWG copper and not longer than 75 feet, using listed connection devices (310.2). Arc-resistant CSST is bonded through the appliance grounding conductor, but if any part of the run lacks that jacket, the full jumper rule applies (310.3).
Metal hangers or straps support the pipe, and pipe is never supported by other piping (407.2). Table 415.1 sets the maximum spacing for steel pipe.
| Steel pipe size | Horizontal spacing |
|---|---|
| 1/2 in. | 6 ft |
| 3/4 or 1 in. | 8 ft |
| 1 1/4 in. or larger | 10 ft (vertical: every floor level) |
CSST follows the manufacturer's spacing. Worked example. A 24 ft straight run of 1/2 inch steel pipe needs supports no more than 6 ft apart: 24 / 6 = 4 spans. The same run in 3/4 inch pipe allows 8 ft: 24 / 8 = 3 spans. Where gas is not dry, piping slopes at least 1/4 inch in 15 feet, with drips at low points (408.1, 408.2).
Valves are approved types matched to the pressure by Table 409.1.1, must be accessible and protected, and are never concealed or placed in a furnace plenum (409.1). Every meter has a valve on its supply side (409.2). In a multiple-tenant building with a common system, each tenant gets a valve and access to it (409.3.1), and a common system serving several buildings has valves outdoors at each building (409.3.2). Each appliance has a shutoff valve in the same room, within 6 feet, ahead of any union, connector or quick-disconnect; a valve behind a movable appliance such as a range counts as accessible (409.5.1). A manifold valve may be up to 50 feet away if permanently identified (409.5.3). A laboratory with two or more gas outlets has one dedicated shutoff by the exit door, signed "Gas Shutoff" (409.6).
In the field
A restaurant rehab in a former retail bay adds a gas range and a fryer. At rough-in, check that the new branch does not cross a return-air plenum, that no valve is buried in the ceiling space, and that CSST passing studs has shield plates. At trim, check the valve within 6 feet in the same room and reachable behind the unit, a listed commercial connector with a restraint on casters, a sediment trap where the appliance needs one, and the bonding jumper if the CSST has no arc-resistant jacket.
Where the appliance has no built-in trap, a sediment trap goes downstream of the appliance shutoff valve, as close to the inlet as practical: a tee with a capped nipple set vertically in its bottom opening (408.4). Illuminating appliances, ranges, clothes dryers, decorative vented appliances, gas fireplaces and outdoor grills need none. The capped nipple may be of any length, or another approved sediment trap device may be used instead. Appliances connect with rigid metal pipe, CSST, semirigid tubing up to 6 feet in the same room, or a listed appliance connector in the same room (411.1). A connector is at most 6 feet long along its centerline and only one serves each appliance (411.1.3.1). Connectors may not be concealed in or pass through walls, floors, partitions, ceilings or appliance housings, with limited exceptions (411.1.3.3), and the valve ahead of a connector is at least as large as the connector (411.1.3.4). A commercial cooking appliance on casters needs a listed connector and a restraining device (411.1.1, 411.1.4).
1. A gas-fired unit heater in a Group S-1 warehouse bay is fed by a branch piped down from the ceiling. Where must its appliance shutoff valve be located under 409.5.1?
2. In a Group B office break room, a gas water heater has no built-in sediment trap. Under 408.4, where does the trap go?
3. In a Group R-2 laundry room, which of these gas appliances is not required to have a sediment trap under 408.4?
4. A restaurant (Group A-2) connects a gas range with a listed appliance connector. Under 411.1.3.1, the maximum overall connector length is:
5. During rough-in of a Group R-2 apartment, a plumber sets a gas shutoff valve inside a wall cavity that will be closed with drywall. Under 409.1.2, this is:
6. Corrugated stainless steel tubing in a light-frame wall of a Group R-2 building runs 1 inch from the stud face that will receive drywall. What protection does 404.7 require?
7. An outdoor gas grill at a community center picnic shelter (Group A-3) is fed by an individual buried line that is approved and not exposed to damage. What is the minimum burial depth under 404.12.1?
8. Exposed gas piping crosses the roof of a Group B building to a rooftop unit. Under 404.9, it must be elevated above the roof surface at least:
9. A Group B office is served by CSST that has no arc-resistant jacket. What is the smallest bonding jumper allowed by 310.2.2?
10. A contractor proposes PVC pipe for a fuel gas branch in a Group R-2 building. Under 403.5, PVC:
11. A horizontal run of 3/4 inch steel gas pipe is being hung in a Group S-2 storage building. Under Table 415.1, the maximum support spacing is:
12. A new gas service must enter a Group B building. Under 404.6, the gas piping:
13. Exposed copper gas tubing runs through a corridor in a Group B building. Under 401.5, it must be identified by:
14. A strip center (Group M) has a common gas piping system serving five tenant spaces. Under 409.3.1, each tenant: