2021 IRC G2413-G2422
Everything so far in this course has been about air: combustion air going in, flue gas going out. This lesson is about the fuel itself, the piping that carries gas from the meter to every appliance in the house. In Texas, plumbers licensed by the Texas State Board of Plumbing Examiners install and test gas piping and connect water heaters; GCHS's role is inspecting, estimating, and managing that licensed work, not doing it. Knowing what a compliant system looks like is still essential for writing an accurate scope of work and for catching a problem before it becomes a call-back.
Steel pipe, galvanized or black, is the default gas piping material and is acceptable under IRC G2414; cast iron pipe is never permitted for fuel gas (G2414.3.1). Copper tubing, Type K or L, may not be used if the gas contains more than an average of 0.3 grain of hydrogen sulfide per 100 standard cubic feet (G2414.4.3), and its joints are made with approved gas tubing fittings, by brazing above 1,000 degrees Fahrenheit, or with listed press-connect fittings rather than ordinary soft solder (G2414.9.2). Corrugated stainless steel tubing, CSST, is permitted throughout the house when installed strictly per its manufacturer's listing, including its specific fittings, shield plates where it lies within 1-1/2 inches of the framing face, and support spacing. Polyethylene (PE) and polyamide (PA) plastic piping is installed outdoors and underground only, with a listed transition fitting to metal piping, and is never run within or under a building or slab (G2415.17.1), apart from narrow exceptions such as anodeless risers; PVC and CPVC are not permitted for fuel gas (G2414.5). Every material choice on a rehab job should be checked against what is actually approved for gas in that jurisdiction; a plumber's supply-house habit is not the same thing as a code citation.
Gas piping in a solid floor must be laid in channels that stay covered but accessible, or run in a Schedule 40 steel, wrought iron, PVC, or ABS conduit (G2415.8). Piping installed underground beneath a building is prohibited unless it is encased in an approved conduit (G2415.14), and a conduit with one end outdoors is sealed at the building end and vented above grade to the outdoors. Piping also may not penetrate a foundation wall below grade; it enters above grade with the annular space sealed (G2415.6). Fittings at concealed locations are limited to threaded elbows, tees, couplings, plugs and caps, brazed or welded fittings, and fittings listed for CSST (G2415.5), so unions and ordinary compression tubing fittings do not qualify, since a concealed leak at a mechanical joint cannot be seen or smelled until it has already migrated somewhere else in the structure. CSST carries an additional, electrical requirement under IRC G2411.2: because a nearby lightning strike or electrical fault can arc through the thin corrugated wall and burn a hole in it, CSST that is not listed with an arc-resistant jacket must be electrically continuous and bonded with a jumper not smaller than 6 AWG copper (or equivalent), connected to the electrical service grounding electrode system. The jumper attaches to a metallic pipe, pipe fitting, or CSST fitting, and its run to the electrode system may not exceed 75 feet (G2411.2.1 to G2411.2.3). CSST listed with an arc-resistant jacket is considered bonded where it connects to an appliance that is connected to the appliance grounding conductor of its circuit (G2411.3), but where any CSST component lacks that jacket, the full G2411.2 bonding applies. An inspector who finds unbonded CSST on a rehab job should treat it as an open item, not a minor omission, since the failure mode is a punctured gas line at a random point along its run.
Before any gas piping is put into service, the whole system, or the section being worked on, must be inspected and pressure tested (G2417.1). IRC G2417.4.1 sets the test pressure at not less than 1.5 times the proposed maximum working pressure, and never less than 3 psig regardless of the system's design pressure, using air, nitrogen, carbon dioxide, or an inert gas as the test medium (G2417.2); oxygen is never used. The test runs for not less than 10 minutes (G2417.4.2), with no drop in pressure, because any reduction shown on the gauge is treated as a leak unless another cause is readily shown (G2417.5). Pressure is read on a manometer or a device calibrated to show a pressure loss, and a mechanical gauge's scale may top out at no more than five times the test pressure (G2417.4), so an oversized gauge cannot show a small leak. Joints stay exposed during the test (G2417.3). A test that "seems fine" after five minutes is not a passed test; the full duration is the point of the requirement, since a slow leak often only shows up as the test continues. The source of pressure is isolated, and appliances that are not part of the test are disconnected or isolated with blanks or caps so the test pressure does not damage them (G2417.3.2).
A sediment trap, sometimes called a drip leg, catches scale, dirt, and moisture carried in the gas stream before it reaches an appliance's valve and burner. Where an appliance does not have one built in, the code (G2419.4) requires a tee fitting with a capped nipple, of any length, installed vertically in the bottom opening of the tee, located as close to the appliance's inlet as practical and downstream of the appliance shutoff valve. A handful of appliance types are exempted because their design or use makes a trap unnecessary or impractical: illuminating appliances, ranges, clothes dryers, decorative vented appliances for vented fireplaces, gas fireplaces, and outdoor grills, along with any appliance whose own trap is already built in. A furnace or a natural-draft water heater is not on that exception list and should have a sediment trap at its connection; its absence is a common, easy-to-miss finding in an older mechanical closet.
Every gas appliance needs its own shutoff valve, separate from any main building or meter valve, located in the same room as the appliance and within 6 feet of it, installed upstream of the union, connector, or quick-disconnect device that serves the appliance under IRC G2420.5.1. Narrow exceptions let the valve for a vented decorative appliance or room heater sit remotely if it is permanently identified and serves only that appliance, and let a manifold valve sit within 50 feet of the appliance it serves (G2420.5.2, G2420.5.3). The valve has to be accessible: a valve behind a movable appliance like a range or a clothes dryer still counts as accessible, but one buried behind finished drywall, inside a sealed chase, or above an inaccessible ceiling does not, no matter where it sits on the line. A listed appliance connector, the flexible metal tubing between the shutoff valve and the appliance itself, may be no longer than 6 feet overall, with only one connector per appliance (G2422.1.2.1), and must not be concealed within or extended through a wall, floor, partition, ceiling, or appliance housing, apart from a few narrow exceptions (G2422.1.2.3); a connector is a serviceable, visible part of the system by design; a hidden one cannot be inspected or safely disconnected for appliance service.
Liquefied petroleum, or LP, gas systems layer a few additional items onto everything above: outdoor above-ground or buried tanks with their own clearance-to-building and clearance-to-ignition-source rules, a pressure-reducing regulator (often two stages) sized and vented per its listing, and piping sized for LP's different pressure and specific gravity characteristics rather than natural gas tables. GCHS project areas along the Gulf Coast are mostly on natural gas utility service, but rural infill and some coastal county rehab work still involves LP tanks, so a scope of work in those areas should note the tank supplier and confirm the regulator and piping were sized for LP specifically, not carried over from a natural gas worksheet.
A worked example on the test: a plumber proposes to test a new gas piping run that will operate at 7 inches water column, roughly 0.25 psi, once in service. IRC G2417.4.1 requires 1.5 times that working pressure, or about 0.4 psi, but the code's 3 psi floor controls because 0.4 psi is far below it. The test must therefore be run at not less than 3 psi and held for 10 minutes with no drop in pressure, regardless of how low the appliance's actual operating pressure will be.
In the field
A common rehab finding is a furnace or water heater installed with no sediment trap and a shutoff valve buried behind a finished wall from an earlier remodel. Neither is a fuel-gas emergency by itself, but both turn a routine appliance swap into an unplanned wall-opening or into scale getting drawn straight into the new appliance's gas valve. GCHS flags both items in the pre-construction scope so the licensed plumber prices the fix into the job instead of discovering it mid-installation.
1. Which piping material is never permitted for fuel gas distribution?
2. Polyethylene (PE) gas piping is permitted:
3. Gas piping installed underground beneath a building is prohibited except where it is:
4. CSST gas piping (not listed with an arc-resistant jacket) must be bonded with a jumper not smaller than:
5. CSST bonding exists primarily to protect against:
6. New gas piping must be pressure tested at not less than:
7. A new gas line will operate at about 0.25 psi in service. What is the minimum required test pressure?
8. The correct test medium for a gas piping pressure test is:
9. A sediment trap is required at a gas appliance connection except for:
10. A sediment trap must be installed:
11. A gas appliance shutoff valve must ordinarily be located:
12. A shutoff valve is installed behind a range that can be pulled out for service. Is this accessible?
13. Under the code's general rule, a listed flexible appliance connector may:
14. Which of these fittings is permitted at a concealed location in a gas piping system?