1 Scope
NOTE This specification covers the materials, fabrication, installation, examination, pressure testing, and purging of field-installed fuel-gas piping conveying natural gas or undiluted liquefied petroleum (LP) gas to gas-fired appliances and equipment. (1.1)
NOTE The work includes interior distribution piping, exterior aboveground piping, buried exterior piping within the property line, manual gas valves, line-pressure regulators and their overpressure protection and venting, sediment traps, appliance shutoff valves and connectors, pipe supports, sleeves and firestopping at penetrations, corrosion protection of buried steel, and the electrical bonding of metallic gas piping. (1.2)
1.3All work shall comply with NFPA 54 / ANSI Z223.1 (National Fuel Gas Code), the adopted edition of the International Fuel Gas Code (IFGC), and, for systems serving LP gas, the applicable provisions of NFPA 58 (Liquefied Petroleum Gas Code).
NOTE Fuel-gas piping carries a flammable fluid through occupied buildings, so the controlling concern of this standard is not flow capacity alone but the integrity and safety of every joint, the reliable function of every regulator and shutoff, and the verification that the completed system is leak-free before it is placed in service. (1.4)
NOTE A water leak makes a stain; a gas leak makes an explosion hazard. (1.5)
NOTE For this reason the way the piping is jointed, pressure-tested, and purged is as much a part of this standard as the materials themselves, and the bonding of metallic piping and the venting of overpressure protection are treated as life-safety requirements rather than incidental details. (1.6)
NOTE The upstream boundary of work under this standard is the outlet of the gas utility's meter (for natural gas) or the outlet of the LP-gas second-stage or integral two-stage regulator (for LP gas). (1.7)
NOTE The utility's service main, meter, and meter-set regulator are the utility's work and are excluded. (1.8)
NOTE The downstream boundary is the appliance shutoff valve and the connector serving each appliance; the appliances and equipment themselves are covered by their own standards, including
Boilers,
Water Heaters, and
Packaged Rooftop Units.
(1.9) 1.10The Contractor shall coordinate the meter location, the delivered service pressure, and the connected appliance load with the serving gas utility before installation, because the available service pressure determines whether line-pressure regulators are required within the building.
2 Referenced Standards
2.1Materials, fabrication, and installation shall comply with the latest adopted editions of the standards and codes listed below.
| Standard |
Title |
| NFPA 54 / ANSI Z223.1 |
National Fuel Gas Code |
| NFPA 58 |
Liquefied Petroleum Gas Code |
| NFPA 70 |
National Electrical Code (bonding of metallic gas piping and CSST) |
| IFGC |
International Fuel Gas Code |
| ASME B31.1 |
Power Piping (where building gas piping is engineered as a power-piping system) |
| ASME B31.9 |
Building Services Piping |
| ASTM A53 |
Pipe, Steel, Black and Hot-Dipped, Zinc-Coated, Welded and Seamless |
| ASTM A106 |
Seamless Carbon Steel Pipe for High-Temperature Service |
| ASME B16.3 |
Malleable Iron Threaded Fittings, Classes 150 and 300 |
| ASME B16.5 |
Pipe Flanges and Flanged Fittings |
| ASME B16.9 |
Factory-Made Wrought Buttwelding Fittings |
| ASTM A234 |
Piping Fittings of Wrought Carbon Steel and Alloy Steel for Moderate and High-Temperature Service |
| ASME B1.20.1 |
Pipe Threads, General Purpose (Inch) |
| ASTM D2513 |
Polyethylene (PE) Gas Pressure Pipe, Tubing, and Fittings |
| ANSI LC 1 / CSA 6.26 |
Fuel Gas Piping Systems Using Corrugated Stainless Steel Tubing (CSST) |
| ASTM B837 |
Seamless Copper Tube for Natural Gas and Liquefied Petroleum (LP) Gas Fuel Distribution Systems |
| ANSI Z21.24 / CSA 6.10 |
Connectors for Gas Appliances |
| ANSI Z21.69 / CSA 6.16 |
Connectors for Movable Gas Appliances |
| ANSI Z21.80 / CSA 6.22 |
Line-Pressure Regulators |
| ASME Sec. IX |
Boiler and Pressure Vessel Code — Welding, Brazing, and Fusing Qualifications |
| MSS SP-58 |
Pipe Hangers and Supports — Materials, Design, Manufacture, Selection, Application, and Installation |
2.2Materials, fabrication, and installation shall comply with the latest adopted editions of the standards and codes listed above.
2.3Where the contract documents, the adopted fuel-gas or building code, the serving utility's requirements, the equipment manufacturer's installation instructions, or a referenced standard conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
3 Submittals
3.1 Action Submittals
NOTE The action submittals required before procurement and installation are the product data, drawings, calculations, qualification records, and test plan listed below. (3.1.1)
- Product data for pipe and tubing, showing the ASTM or ANSI/CSA designation, schedule or wall, size range, and coating where applicable for each material proposed (steel, polyethylene, CSST, or copper)
- Product data for fittings and joining materials, including malleable-iron threaded fittings, welded fittings, flanges, joint compound or tape rated for fuel gas, CSST fittings and termination devices, and heat-fusion or mechanical fittings for polyethylene
- Product data for each manual gas valve, showing the valve type, the body and seat materials, the pressure rating, and the listing to a recognized gas-valve standard
- Product data for each line-pressure regulator, showing the inlet and outlet pressure range, the capacity, the relief or overpressure-protection method, the vent connection, and the listing to ANSI Z21.80 / CSA 6.22
- Product data for appliance connectors, showing the ANSI Z21.24 / CSA 6.10 (or Z21.69 / CSA 6.16) listing, length, and capacity
- A gas piping layout drawing showing routing, pipe sizes, pressure tiers and regulator locations, valve and sediment-trap locations, support locations, sleeve and firestop locations, buried-piping depth and tracer-wire routing, and the connected load at each appliance, coordinated against the available service pressure
- Pipe-sizing calculations demonstrating that each section delivers the required volume within the allowable pressure drop for the system pressure tier and the longest-length or branch-length method used, per NFPA 54
- Welding procedure specifications (WPS) and procedure qualification records (PQR) per ASME Section IX, and welder performance qualification records, where any field-welded joints are used
- Polyethylene heat-fusion procedure and operator qualification records where PE piping is used
- A written pressure-test and purging plan describing the test medium, test pressure and hold duration by pressure tier, the instrument used, the leak-test method, the witness, and the indoor/outdoor purging procedure
☐ Pipe and tubing product data (steel, PE, CSST, or copper)
☐ Fitting and joining-material product data
☐ Manual gas valve product data
☐ Line-pressure regulator product data (ANSI Z21.80)
☐ Appliance connector product data (ANSI Z21.24)
☐ Gas piping layout and pressure-tier drawing
☐ Pipe-sizing calculations per NFPA 54
☐ Welding procedure and welder qualification records
☐ Polyethylene fusion procedure and operator qualification records
☐ Pressure-test and purging plan
3.1.2The Contractor shall submit the action submittals listed above for the Engineer's review and return before procurement and installation.
3.1.3Action submittals shall be complete and internally coordinated with the serving utility's delivered pressure and the connected appliance loads before any item is submitted.
3.2 Closeout Submittals
NOTE The closeout submittals required before the gas systems are accepted and placed in service are the test reports, records, verifications, drawings, and maintenance data listed below. (3.2.1)
- Signed and dated pressure-test reports for each system or section, recording the test medium, the test pressure, the hold duration, the instrument and its calibration, the witness, and the pass/fail determination
- A purging record documenting that each section was purged of air before being placed in service and that appliances were lit and verified
- Bonding verification documenting that metallic gas piping and CSST are bonded in accordance with NFPA 70, including the bonding-jumper size and the point of connection to the grounding electrode system
- As-built piping drawings reflecting actual routing, sizes, pressure tiers, regulator and valve locations, buried-piping depth, and tracer-wire routing
- Operation and maintenance data for line-pressure regulators and for any automatic shutoff or excess-flow devices, including the relief or overpressure setting
☐ Signed and dated pressure-test reports for each system or section
☐ Purging record (each section purged; appliances lit and verified)
☐ Bonding verification for metallic gas piping and CSST per NFPA 70
☐ As-built piping drawings (routing, sizes, pressure tiers, regulator/valve locations, buried depth, tracer wire)
☐ Operation and maintenance data for line-pressure regulators and shutoff/excess-flow devices
3.2.2At substantial completion, the Contractor shall provide the closeout submittals listed above before the gas systems are accepted and placed in service.
4 Quality Assurance
4.1 Code Compliance
4.1.1All fuel-gas piping shall comply with NFPA 54 / ANSI Z223.1 (and NFPA 58 for LP-gas systems) for materials, sizing, joints, installation, testing, and purging, and with the adopted IFGC.
4.1.2The Contractor shall maintain a copy of the applicable fuel-gas code at the project site throughout installation.
4.1.3Where the serving utility imposes requirements more stringent than the code, the utility's requirements shall govern for piping upstream of the building.
4.2 Welder and Fusion-Operator Qualifications
4.2.1Personnel performing field-welded steel joints shall be qualified under ASME Section IX for the welding procedure, position, and material being welded, and qualification records shall be available at the site.
4.2.2Personnel performing heat-fusion joints on polyethylene gas pipe shall be qualified under a written fusion procedure and shall hold current qualification for the fusion method and equipment used.
4.2.3The Contractor shall not allow unqualified personnel to make production joints; rework of joints made by unqualified personnel is at the Contractor's expense.
4.3 CSST Installer Qualifications
NOTE CSST fitting assembly, bend radius, support, and bonding are system-specific, and a defective CSST fitting is a concealed leak source, so CSST installation is restricted to personnel trained and certified by the tubing manufacturer. (4.3.1)
4.3.2Corrugated stainless steel tubing shall be installed only by personnel who have completed the CSST manufacturer's training program and hold current certification.
4.3.3CSST installer certification records shall be available at the site.
4.4 Utility and AHJ Coordination
4.4.1The Contractor shall coordinate the meter location, the delivered service pressure, the connected load, and the inspection sequence with the serving gas utility and the authority having jurisdiction before rough-in.
4.4.2The pressure test shall be witnessed by the authority having jurisdiction (or the Engineer where the jurisdiction delegates witnessing), and the system shall not be concealed, insulated, or placed in service until the test has been witnessed and accepted.
5 Environmental and Service Conditions
5.1 Delivered Service Pressure
NOTE The delivered service pressure determines the system pressure tier and whether line-pressure regulators are required within the building. (5.1.1)
NOTE A low delivered pressure forces larger pipe to carry the same load within the allowable pressure drop; an elevated delivered pressure allows smaller pipe but requires line-pressure regulators with overpressure protection at the point of pressure reduction. (5.1.2)
7 in. w.c. (nominal low-pressure natural-gas service)
2 psig (elevated natural-gas service)
5 psig (elevated natural-gas service)
11 in. w.c. (nominal LP-gas service downstream of second-stage regulator)
5.1.3The gas pressure delivered at the meter outlet (natural gas) or at the second-stage regulator outlet (LP gas) shall be confirmed with the serving utility.
5.2 Piping Environment
NOTE The piping environment governs material selection and corrosion protection. (5.2.1)
NOTE Interior piping is dry and accessible. (5.2.2)
NOTE Exterior aboveground piping is exposed to weather and ultraviolet light. (5.2.3)
NOTE Buried piping is exposed to soil moisture and corrosive soils and is the principal corrosion concern for steel. (5.2.4)
☐ Interior, concealed or exposed, dry
☐ Exterior aboveground, exposed to weather and UV
☐ Buried exterior, within property line
☐ Wet, corrosive, or coastal exposure
5.2.5The Contractor shall identify the environment for each section and select materials and coatings accordingly.
6 System Pressure and Materials
NOTE The system pressure tier is the single most consequential decision in a fuel-gas system, because it cascades into pipe size, regulator requirements, overpressure protection, and test pressure. (6.1)
NOTE A low-pressure system operating at or below ½ psig (about 7 to 14 in. w.c.) delivers gas to appliances at the pressure they require without any in-building regulation beyond what the meter set provides, so it is the simplest system and the default for most light-commercial and residential work. (6.2)
6.3An elevated-pressure system operating at 2 psig or 5 psig carries the same load in smaller pipe, which is valuable on long runs and high-rise risers, but each branch serving an appliance must drop to appliance pressure through a line-pressure regulator equipped with overpressure protection.
NOTE The elevated-pressure approach trades smaller, cheaper pipe for the added cost, venting, and maintenance of distributed regulators. (6.4)
○ Low pressure, ≤ ½ psig (≈ 7-14 in. w.c.) — no in-building regulation (standard)
○ Elevated pressure, 2 psig — line-pressure regulators at branches
○ Elevated pressure, 5 psig — line-pressure regulators at branches
6.5 Pipe Material by Location
NOTE Schedule 40 black steel is the standard for interior distribution and exposed aboveground piping because it is strong, threadable or weldable, and economical; it is not used buried without coating because bare steel corrodes in soil. (6.5.1)
6.5.2Polyethylene to ASTM D2513 is the standard for buried exterior piping because it does not corrode, but it shall not be used inside a building or aboveground except in the short shielded transition at an anodeless riser.
NOTE CSST is used for concealed interior runs where its flexibility and speed of installation are valuable, subject to the bonding requirement of this standard. (6.5.3)
6.5.4Copper to ASTM B837 may be used for interior piping only where the gas does not contain more than an average of 0.3 grains of hydrogen sulfide per 100 standard cubic feet, because sulfur in the gas attacks copper and forms copper sulfide scale that flakes loose and plugs valves and orifices.
☐ Schedule 40 black steel (ASTM A53) — interior distribution and exposed aboveground
☐ Polyethylene (ASTM D2513) — buried exterior only, with anodeless riser
☐ CSST (ANSI LC 1 / CSA 6.26) — concealed interior runs, bonded per NFPA 70
☐ Copper (ASTM B837) — interior, only where gas sulfur content permits
6.5.5The pipe material shall be selected for the service and location.
6.6 Pipe Sizing
NOTE Sizing is not a place for conservatism by oversizing: an oversized low-pressure system wastes material, while an undersized system starves appliances at peak demand and produces nuisance flame failures that are difficult to diagnose. (6.6.1)
NOTE The allowable pressure drop depends on the tier. (6.6.2)
NOTE A low-pressure system is conventionally sized for a drop of about 0.5 in. w.c. across the longest run so that every appliance sees adequate pressure at full demand; an elevated-pressure system tolerates a larger drop, in psi, because the line-pressure regulators restore appliance pressure at each branch. (6.6.3)
○ Longest-length method per NFPA 54 (standard)
○ Branch-length method per NFPA 54
○ Manufacturer's sizing tables (CSST)
0.3 in. w.c. — conservative, long or heavily loaded runs
0.5 in. w.c. — standard low-pressure sizing
1.0 in. w.c. — short runs with ample inlet pressure
6.6.4Pipe sizes shall be determined by an accepted NFPA 54 sizing method (the longest-length method, the branch-length method, or the manufacturer's sizing tables for CSST) for the connected appliance load, the specific gravity of the gas, the system pressure tier, and the allowable pressure drop.
6.6.5The connected load at each appliance, and the total demand at the meter, shall be the actual input ratings of the served equipment, not assumed values.
6.7 Joint Method
○ Threaded joints (ASME B1.20.1) with fuel-gas-rated joint compound, sizes through 2 in. (standard)
○ Welded joints (ASME Section IX qualified) for sizes larger than 2 in. or elevated pressure
○ Flanged joints (ASME B16.5) at equipment and where disassembly is required
6.8 Valve Type
○ Listed gas ball valve, full-port, for sizes through 2 in. (standard)
○ Lubricated plug valve for larger sizes and elevated pressure
7 Pipe, Fittings, and Joints
7.1 Steel Pipe and Fittings
NOTE Galvanized steel offers no advantage indoors and is avoided where the zinc coating can flake into the gas stream. (7.1.1)
NOTE Cast iron is brittle and can fracture, so cast-iron threaded fittings are not used in gas piping. (7.1.2)
7.1.3Steel gas pipe shall be standard-weight (Schedule 40) black steel conforming to ASTM A53 or ASTM A106.
7.1.4Galvanized steel may be used for gas pipe where its use offers no disadvantage and the zinc coating will not flake into the gas stream.
7.1.5Threaded fittings shall be malleable iron conforming to ASME B16.3.
7.1.6Cast-iron threaded fittings shall not be used in gas piping.
7.1.7Welded fittings shall be wrought carbon steel conforming to ASTM A234 and ASME B16.9.
7.1.8Flanges shall conform to ASME B16.5.
7.2 Threaded Joints
NOTE Ordinary pipe-dope and tape soften and wash out in the presence of gas-borne liquids and leak, so only joint compound or tape listed as resistant to the fuel gas is permitted, and it is applied to the male threads only so it is not pushed into the bore. (7.2.1)
7.2.2Threaded joints shall be cut to ASME B1.20.1 (NPT) taper threads.
7.2.3Threaded joints shall be made up with a joint compound or tape listed as resistant to the action of the fuel gas, and to LP gas where applicable.
7.2.4Joint compound or tape shall be applied to the male threads only so that compound is not pushed into the bore.
7.2.5Threads shall be clean and full.
7.2.6Over-cut or wrench-damaged threads shall not be made up.
7.2.7Pipe-dope or tape not rated for fuel gas shall not be used.
7.3 Welded Joints
NOTE Welding is required where the elevated-pressure tier or the pipe size makes threaded joints impractical, and is preferred for concealed and inaccessible piping because a welded joint has no thread leak path. (7.3.1)
7.3.2Welded joints shall be made by welders qualified under ASME Section IX following a qualified procedure.
7.3.3Backing rings shall not obstruct the bore.
7.4 Polyethylene Pipe and Joints
7.4.1Polyethylene pipe and fittings shall conform to ASTM D2513.
7.4.2Polyethylene pipe shall be joined by heat fusion (butt, socket, or electrofusion) by qualified operators, or by mechanical fittings listed for PE gas pipe.
7.4.3PE pipe shall be marked and used only underground.
7.4.4Where PE pipe transitions to aboveground steel, the transition shall be made below grade with a factory-assembled anodeless riser that shields the PE from mechanical and ultraviolet damage, so that no PE is exposed above grade.
7.5 CSST
7.5.1Corrugated stainless steel tubing shall conform to ANSI LC 1 / CSA 6.26.
7.5.2CSST shall be installed with the manufacturer's listed fittings, struck up to the manufacturer's torque.
7.5.3CSST shall be supported, and protected at penetrations and where subject to physical damage with the manufacturer's striker plates.
7.5.4CSST shall not be installed where it can be subjected to excessive movement, abrasion, or concealed mechanical damage without protection.
7.5.5CSST shall be bonded in accordance with the bonding requirements of this standard regardless of whether it is listed with an arc-resistant jacket.
7.6 Copper Tube
7.6.1Where permitted by the gas sulfur content, copper tube shall conform to ASTM B837.
7.6.2Copper tube shall be jointed by brazing, by approved flared fittings, or by listed press fittings rated for fuel gas.
7.6.3Copper shall not be used for LP gas in the vapor phase where prohibited by the AHJ.
7.6.4Copper shall not be used where the gas is not affirmatively known to contain 0.3 grains or less of hydrogen sulfide per 100 standard cubic feet.
8 Valves, Regulators, and Overpressure Protection
8.1 Manual Gas Valves
NOTE Ball valves with a full port and a fuel-gas listing are standard for sizes through 2 in.; lubricated plug valves are used for larger sizes and elevated pressure. (8.1.1)
NOTE Providing valves at risers and sectional isolation points lets the system be shut down for service without de-gassing the entire building. (8.1.2)
☐ Appliance shutoff valve at each appliance
☐ Valve at base of each riser
☐ Valve at each building entry / meter outlet
☐ Sectional valves for floor or tenant isolation
8.1.3Each manual gas valve shall be listed for fuel-gas service and rated for the system pressure.
8.1.4A valve serving a single appliance shall be the appliance shutoff valve described under Appliance Shutoff Valve.
8.1.5Valves shall be provided at the base of each riser and at points required for sectional isolation so the system can be shut down for service without de-gassing the entire building.
8.2 Line-Pressure Regulators
7 in. w.c. — natural-gas appliances
11 in. w.c. — LP-gas appliances
Other, per appliance manifold requirement
8.2.1Where the system operates at an elevated pressure (2 psig or 5 psig), each branch serving appliances shall reduce to appliance pressure through a line-pressure regulator listed to ANSI Z21.80 / CSA 6.22 and sized for the branch load and the inlet-to-outlet pressure drop.
8.2.2An accessible manual shutoff valve shall be installed upstream of each regulator so the regulator can be isolated for service.
8.2.3The regulator outlet pressure shall match the appliance manifold pressure requirement, typically about 7 in. w.c. for natural gas and 11 in. w.c. for LP gas, confirmed against the served appliances.
8.3 Overpressure Protection
NOTE This is a life-safety requirement: an unprotected regulator failure can over-fire appliances and rupture low-pressure components, exposing downstream piping and appliance controls to the full upstream pressure, which they are not rated to withstand. (8.3.1)
○ Internal relief integral to the line-pressure regulator (standard for small branch loads)
○ Separate downstream relief valve
○ Series (monitoring) regulator
○ Automatic overpressure shutoff device
8.3.2Each line-pressure regulator shall be provided with overpressure protection so that a failure of the regulator cannot expose downstream piping and appliance controls to the full upstream pressure.
8.3.3Overpressure protection shall be by an internal relief device integral to the regulator, a separate downstream relief valve, a monitoring (series) regulator, or an automatic shutoff device, selected so the downstream pressure cannot exceed the limit established by NFPA 54 for the served appliances.
8.4 Regulator and Relief Venting
○ Outdoors, downward-facing screened terminal, ≥ 3 ft from openings and ignition sources (standard)
○ Vent-limiting device listed for the regulator in lieu of outdoor vent line (small regulators where permitted)
8.4.1The vent of each line-pressure regulator and of each relief device shall terminate outdoors in a safe location, fitted with a screened, downward-facing, weather-protected terminal to keep out water, insects, and debris that would block the vent and prevent the regulator from breathing.
8.4.2The vent terminal shall be located not less than 3 ft from any building opening and not less than 3 ft from any source of ignition, so that gas discharged on a relief event disperses outdoors rather than entering the building.
9 Sediment Traps and Appliance Connections
9.1 Sediment Traps
NOTE The trap protects the appliance's gas valve, which is the most failure-sensitive component on the appliance: scale, moisture, and pipe debris carried by the gas drop into the dead leg rather than reaching the appliance gas valve and burner orifices, where they would cause erratic operation and nuisance shutdowns. (9.1.1)
○ Tee with capped drip nipple at each appliance, downstream of the shutoff valve (standard)
○ Omitted only where the appliance is listed with an integral sediment trap or the manufacturer prohibits one
9.1.2A sediment trap shall be installed downstream of the appliance shutoff valve and as close to the appliance inlet as practical, except where the appliance manufacturer's instructions exclude it or the appliance is equipped with one.
9.1.3The sediment trap shall be a tee with a capped nipple in the bottom outlet, or another device recognized as an effective trap.
9.2 Appliance Shutoff Valve
9.2.1An accessible manual shutoff valve shall be installed in the same room as, within 6 ft of, and ahead of the connector serving each appliance, so the appliance can be isolated for service without shutting down the building.
9.3 Appliance Connectors
○ Rigid pipe connection (standard for fixed appliances)
○ Listed flexible appliance connector (ANSI Z21.24) for movable or vibration-isolated appliances
9.3.1Where a listed flexible appliance connector is used to make the final connection to a movable or vibration-isolated appliance, it shall conform to ANSI Z21.24 / CSA 6.10, or to Z21.69 / CSA 6.16 for movable appliances.
9.3.2A flexible appliance connector shall be sized for the appliance input.
9.3.3A flexible appliance connector shall be installed without concealment, without passing through a wall, floor, or partition, and without being joined to another connector in series.
10 Corrosion Protection and Bonding
10.1 Buried Steel Corrosion Protection
NOTE Soil moisture drives galvanic corrosion that will perforate bare steel. (10.1.1)
NOTE The preferred practice for new buried gas piping is to avoid buried steel altogether by using polyethylene with an anodeless riser, which needs no coating or cathodic protection. (10.1.2)
○ Buried steel avoided — PE pipe with anodeless riser used instead (preferred)
○ Factory dielectric coating, holiday-tested, with sacrificial-anode cathodic protection
○ Factory dielectric coating with impressed-current cathodic protection and test station
10.1.3Buried steel gas piping shall be protected against corrosion by a factory-applied bonded dielectric coating.
10.1.4The dielectric coating shall be inspected for holidays and repaired before backfill.
10.1.5Where buried steel is used in a corrosive soil or where required by the utility, cathodic protection (sacrificial anodes or an impressed-current system) shall be provided and a test station installed so the protection can be verified over the life of the system.
NOTE Bonding gives a fault current or a lightning surge a low-impedance path to ground instead of arcing across a pipe joint, where the arc energy can burn through the pipe wall and ignite the gas. (10.2.1)
10.2.2Metallic gas piping that may become energized shall be electrically continuous and bonded to the building grounding electrode system in accordance with NFPA 70.
10.2.3The bonding connection shall be made with a listed clamp at a point where the piping is accessible.
10.3 Bonding of CSST
NOTE Corrugated stainless steel tubing requires a dedicated bonding connection because its thin corrugated wall is far more vulnerable to arc perforation than rigid steel pipe: a nearby lightning strike can energize the tubing and burn a pinhole through the wall, releasing gas. (10.3.1)
○ Dedicated 6 AWG copper bonding jumper to grounding electrode system, listed clamps (standard)
○ Bonding per CSST manufacturer's listing for arc-resistant jacketed product, plus system bond to grounding electrode
10.3.3The bonding jumper for CSST shall be not smaller than 6 AWG copper, shall connect to the steel gas-pipe segment at the meter outlet or the point the manufacturer specifies, and shall terminate on the grounding electrode system, all with listed bonding clamps in accordance with NFPA 70.
10.3.4CSST listed with an arc-resistant jacket to ANSI LC 1 / CSA 6.26 may have different supplemental-bonding allowances, but the system bonding to the grounding electrode is required in all cases.
11 Identification
NOTE Aboveground gas piping is identified so that anyone working near it knows it carries fuel gas and can trace it to its shutoff. (11.1)
☐ Legend marker with directional flow arrow at intervals and at penetrations
☐ Identification at each valve and regulator
☐ Distinguishing color band where multiple services share a space
11.2Aboveground gas piping shall be identified so that anyone working near it knows it carries fuel gas and can trace it to its shutoff.
11.3Piping shall be marked with the legend and a directional flow arrow at intervals along each run, at each side of a wall or floor penetration, and at each valve and regulator, in accordance with Equipment Labeling. 11.4In areas where the building has multiple piped services, gas piping shall be distinguished by color or banding from water, compressed air, and other services so it is not mistaken for another system.
12 Installation
12.1 General
12.1.1The Contractor shall install all gas piping in accordance with this standard, the contract drawings, NFPA 54 (and NFPA 58 for LP gas), and the equipment manufacturer's installation instructions.
12.1.2Where these conflict, the more stringent governs.
12.1.3Open pipe ends shall be capped or plugged whenever work stops so that debris and moisture do not enter the bore.
12.2 Routing
12.2.1Gas piping shall be routed as indicated on the gas piping drawings and shall take the most direct practical path consistent with support, access to valves, and avoidance of prohibited locations. 12.2.2Piping shall not be run where it bears on or is supported by other piping, and shall be installed so that condensate cannot collect in low points without a drip; where a low point is unavoidable a drip leg shall be provided at an accessible location where the condensate will not freeze.
12.3 Support Spacing
½ in. — 6 ft; ¾ in. and 1 in. — 8 ft; 1¼ in. and larger — 10 ft (per NFPA 54)
Closer spacing where indicated on drawings
12.3.1Piping shall be supported in accordance with MSS SP-58 and the spacing limits of NFPA 54, with supports at every change of direction and at each valve and regulator.
12.3.2For steel pipe the maximum horizontal spacing is 6 ft for ½ in., 8 ft for ¾ in. and 1 in., and 10 ft for 1¼ in. and larger.
12.3.3Vertical steel piping shall be supported at every floor level.
12.3.4CSST shall be supported at the intervals in the CSST manufacturer's instructions.
12.3.5Supports shall not abrade the pipe coating or, on CSST and copper, the tubing wall.
12.4 Sleeves Through Walls and Floors
12.4.1Gas piping passing through a wall, floor, or roof shall be installed in a sleeve sized to pass the pipe without contact, so the pipe is not abraded or stressed by the structure and can be inspected and replaced.
12.4.2Where a gas line passes through a foundation wall below grade, it shall be sleeved and the annular space sealed against gas and water entry; a buried gas line shall not pass directly under a building, and where it must enter, it shall be sleeved and vented to the outside per NFPA 54 so any leaking gas is carried out of the structure rather than collecting beneath it.
12.5 Below-Grade Installation
1224
121824
Default: 12 in.
12.5.1Buried gas piping shall be installed with not less than 12 in. of cover, increased to not less than 18 in. where external damage is likely (such as under a driveway).
12.5.2An electrically continuous, corrosion-resistant tracer wire of not less than 14 AWG insulated copper shall be buried with non-metallic (PE) pipe and brought up at an accessible point so the line can be located after backfill.
12.5.3The transition from buried PE to aboveground steel shall be made with a factory anodeless riser.
12.5.4A continuous 14 AWG (minimum) insulated copper tracer wire shall be buried with all non-metallic gas pipe and terminated accessibly aboveground.
12.6 Seismic Bracing
12.6.1Where the project is in a seismic design category that requires it, gas piping shall be braced against seismic movement and shall be provided with flexible connections where it crosses a seismic joint or connects to equipment that can move relative to the piping, so that ground motion does not fracture a joint and release gas.
12.6.2Seismic bracing shall be coordinated with the supports and shall not transfer load into threaded joints.
12.7 Prohibited Locations
12.7.1Gas piping shall not be run in or through a duct, plenum, chimney, gas vent, elevator shaft, dumbwaiter, or air-handling enclosure used to convey other than combustion air, nor concealed in a solid partition or wall except where the material is listed for concealment (such as CSST or coated steel installed per the code).
12.7.2Unions, swing joints, and other concealed fittings that cannot be tested in place shall not be installed in inaccessible locations.
13 Field Quality Control / Testing
13.1 Pressure Test
○ Air (standard)
○ Nitrogen or other inert gas
3100
3102550100
Default: 3 psig
13.1.1Before being concealed, insulated, or placed in service, the gas piping system (or an isolated section) shall be pressure-tested with air, nitrogen, carbon dioxide, or another inert gas.
13.1.2Fuel gas and oxygen shall never be used as the test medium.
13.1.3Appliances, regulators, and any device not rated for the test pressure shall be isolated or removed and the openings plugged before the test, then reconnected and leak-checked at operating pressure afterward.
13.1.4The test pressure shall be not less than 1.5 times the proposed maximum working pressure but not less than 3 psig, applied with a gauge or recorder of appropriate range and resolution.
13.1.5The pressure source shall be isolated for the hold period so the test measures the piping and not the source.
13.2 Hold Duration
101440
1030601204801440
Default: 30 minutes
13.2.1The pressure shall be held, with no measurable drop attributable to leakage, for the duration required by NFPA 54: not less than ½ hour for each 500 ft³ of pipe volume or fraction thereof, except that a system smaller than 10 ft³ in volume (or a single-family dwelling) shall be held not less than 10 minutes, and no test is required to exceed 24 hours.
13.2.2Any drop not attributable to ambient temperature change indicates a leak, which shall be located and corrected and the section re-tested.
13.2.3A test gauge reading shall be temperature-corrected before the result is judged, because the test gas pressure shifts with temperature independently of any leak.
13.3 Leak Test of Joints Made or Exposed After the Pressure Test
○ Noncorrosive leak-detection solution at each joint (standard)
○ Calibrated combustible-gas detector
13.3.1Joints made or re-opened after the system pressure test (for example, the final connection to a regulator or appliance), and the system as a whole at operating pressure once gas is introduced, shall be leak-tested at operating pressure with a noncorrosive leak-detection solution or an approved gas detector.
13.3.2A flame shall never be used to test for leaks.
13.4 Purging
○ Purge to outdoors at an accessible point away from ignition sources (standard)
○ Purge small interior volumes to a point of combustion with continuous attention, per NFPA 54
13.4.1After the pressure test is accepted and before appliances are lit, each section shall be purged of air at the time it is placed in service so that no flammable air-gas mixture remains in the piping.
13.4.2Purging shall discharge to the outdoors, or where small interior volumes are purged to a point of combustion, it shall be done with continuous attention and with ignition sources controlled, in accordance with NFPA 54.
13.4.3Large-volume and elevated-pressure piping shall be purged outdoors.
13.4.4After purging, each appliance shall be lit and its operation verified before the system is turned over.
14 Cleaning and Protection
14.1The interior of the piping shall be kept clean, dry, and free of cuttings, scale, and moisture throughout installation; open ends shall be capped when work stops.
14.2Before final connection, each line shall be blown clear with the inert test medium or compressed air to expel debris that would otherwise reach appliance valves and sediment traps.
14.3After acceptance, valves and regulators shall be protected from physical damage and from paint or insulation that would obscure their identification or block a vent.
15 Warranty
15.1The Contractor shall warrant the gas piping installation against leaks and against defects in materials and workmanship for a period of not less than one year from substantial completion, or for the period stated in the contract documents if longer.
15.2Any leak attributable to a field joint, any regulator or overpressure device that fails to perform as specified, and any corrosion failure of buried steel within the warranty period shall be corrected at the Contractor's expense, including the cost of locating the leak, repairing the piping, re-testing, and re-purging the affected section.