10.2 Gas Piping Support, Protection, Prohibited Locations & Concealed Piping

10.2 Gas Piping Support, Protection, Prohibited Locations & Concealed Piping

Quick Answer: IFGC 2018 Table 415.1 sets gas pipe support spacing at 6 feet for 1/2-inch steel pipe, 8 feet for 3/4-inch and 1-inch steel pipe, and 10 feet for 1-1/4-inch and larger horizontal steel pipe. Vertical steel pipe 1-1/4 inch and larger is supported at every floor level, and CSST spacing comes from the manufacturer's instructions, not from the table.

Gas Appliances and Piping is 40 of the 100 scored questions on the Maryland Journey Plumber/Gas Fitter exam — the largest domain by a wide margin — and the installation rules in IFGC (International Fuel Gas Code) 2018 Chapter 4 are where most of those points live. This section covers Sections 404, 407 and 415: how gas piping is held up, where it may never go, and what the rules become once the pipe disappears behind drywall.

Support: Materials, Anchoring and Table 415.1

Section 407.2 lists exactly what may carry the weight: metal pipe hooks, metal pipe straps, metal bands, metal brackets, metal hangers or building structural components, suitable for the size of piping and of adequate strength and quality. Three clauses inside that one paragraph generate exam questions:

• Supports must be located at intervals that prevent or damp out excessive vibration.
• Piping must be anchored to prevent undue strains on connected appliances — and it shall not be supported by other piping. Strapping a new 1/2-inch gas branch to an existing 2-inch water line is a violation no matter how solid that water line feels.
• Hangers and supports shall conform to MSS SP-58, must not interfere with free expansion and contraction of the pipe between anchors, and must be designed so they cannot be disengaged by movement of the pipe they carry.

Spacing itself is set by Section 415.1 and Table 415.1.

Table 415.1 — Support of Piping (IFGC 2018)

Three notes decide most questions built on this table:

1. The tubing column is outside diameter (O.D.), not nominal size. Copper tube runs 1/8 inch larger on the outside than its nominal size, so 1/2-inch nominal copper tube is 5/8-inch O.D. and is supported every 6 feet, not the 4 feet printed on the "1/2" row. That 1/2-inch O.D. row describes 3/8-inch nominal tube.
2. Vertical piping is not a distance. For both steel and tubing, vertical runs are supported at every floor level regardless of size.
3. CSST (corrugated stainless steel tubing) is deliberately absent. Section 415.1 sends CSST support spacing to the CSST manufacturer's instructions, which are typically far more frequent than 10 feet.

Worked Support Examples

A 34-foot horizontal run of 1-1/4-inch black steel: Table 415.1 caps spacing at 10 feet. 34 ÷ 10 = 3.4, so three spaces will not work (34 ÷ 3 = 11.33 feet, over the limit). Round the number of spaces up to 4: 34 ÷ 4 = 8.5 feet between supports, which is 5 support points including both ends.

A 30-foot horizontal run of 3/4-inch steel: the cap is 8 feet. 30 ÷ 8 = 3.75 → round up to 4 spaces → 30 ÷ 4 = 7.5 feet apart, again 5 support points.

A 1-1/2-inch steel riser serving three floors: the 10-foot figure never applies. The riser is supported at each of the three floor levels. Always round the number of spaces up, never the spacing, or you will land above the table maximum.

Prohibited Locations (404.3)

Gas piping shall not be installed in or through:

• a ducted supply, return or exhaust
• a clothes chute
• a chimney or gas vent
• a dumbwaiter or elevator shaft

The logic is consistent: each of these is either a moving-air path that would distribute leaking gas through the building, a flue carrying hot combustion products, or a shaft with moving machinery that can shear a pipe. IFGC 2018 adds a townhouse rule to the same section — piping installed downstream of the point of delivery (the outlet of the meter or service regulator, where the utility's responsibility ends and yours begins) shall not extend through any townhouse unit other than the unit served by that piping. A neighbor must never be able to cut, crush or unknowingly modify your customer's gas line.

Piping in Solid Partitions and Walls (404.4)

Concealed piping — piping in a location that becomes inaccessible after the building is finished — shall not be located in solid partitions and solid walls unless it is installed in a chase or casing. "Solid" here means a masonry, concrete or solid-core assembly with no stud cavity. Grouting a gas line directly into block is prohibited; running it through a formed chase or a sleeve inside that same wall is permitted, because the pipe can then be removed or replaced and any leak has a path out.

Fittings in Concealed Locations (404.5) — read the 2018 wording

This section was rewritten for the 2018 edition, and the change matters because the exam is open book to IFGC 2018. Earlier editions wrote the rule as a prohibition: concealed portions of a piping system shall not have unions, tubing fittings, right and left couplings, bushings, compression couplings, or swing joints made by combinations of fittings. The 2018 edition inverts it into a permitted list. Fittings installed in concealed locations are limited to:

1. Threaded elbows, tees and couplings
2. Brazed fittings
3. Welded fittings
4. Fittings listed to ANSI LC-1/CSA 6.26 or ANSI LC-4/CSA 6.32 (the CSST and plastic-piping-component standards)

The outcome is the same and the test is cleaner: if a fitting is not a threaded elbow, tee or coupling, not brazed, not welded, and not listed for concealed use, it may not be concealed. Unions, ground-joint unions, compression couplings, flare fittings, bushings, right-and-left couplings and swing joints assembled from combinations of fittings all fail the list. Separately, Section 409.1.2 prohibits shutoff valves in concealed locations and in furnace plenums, so a valve buried above a hard ceiling is a violation on its own terms.

Note what the section does not say: piping itself may be concealed. What is restricted is the kind of joint you leave inside the assembly, because a joint you cannot reach is a joint you can never re-tighten or leak-test.

Outlets and Obstructions (404.15, 404.16, 404.19)

Gas outlets that do not connect to an appliance shall be capped gas tight (404.15), with an exception for listed flush-mounted quick-disconnect devices and listed gas convenience outlets. Under 404.16, the unthreaded portion of a piping outlet must extend not less than 1 inch through finished ceilings and walls and not less than 2 inches above floors, outdoor patios and slabs. The outlet fitting must be securely supported, outlets shall not be placed behind doors, and outlets must be located in the room or space where the appliance is installed. Finally, 404.19 prohibits placing any device inside piping or fittings that reduces the cross-sectional area or obstructs free gas flow, excepting approved gas filters and approved devices where the system was sized to absorb their pressure drop.

Protection Against Physical Damage (404.7)

Exam Trap: Candidates memorize "gas pipe needs striker plates" and then apply it to everything. Section 404.7 carries a blanket exception: black steel piping and galvanized steel piping are not required to be protected. The plate rule exists for materials a drywall screw or trim nail can actually pierce — copper tube, CSST, semirigid tubing — not Schedule 40 black iron. The second half of the trap is mixing up the two dimensions: 1-1/2 inches is the trigger distance from the framing member face, and 4 inches is how far the plate extends past the framing member. Answer choices that swap them, or that offer "2 inches to each side," are the standard distractors.

Where piping will be concealed within light-frame construction assemblies, it must be protected against penetration by fasteners in accordance with 404.7.1 through 404.7.3.

• 404.7.1 — Piping through holes or notches. Where piping runs through holes or notches in framing members and sits less than 1-1/2 inches from the framing member face to which the wall, ceiling or floor membrane will be attached, the pipe must be protected by shield plates covering the width of the pipe and the framing member and extending not less than 4 inches to each side of the framing member. Where that member is a bottom plate, bottom track, top plate or top track, the plate covers the member and extends not less than 4 inches above the bottom member or 4 inches below the top member.
• 404.7.2 — Piping installed in other locations. Piping located within a framing member and less than 1-1/2 inches from the membrane face, or located outside a framing member and less than 1-1/2 inches from the nearest edge of that face, must be protected by shield plates covering the width and length of the piping.
• 404.7.3 — Shield plates. Steel, thickness not less than 0.0575 inch (No. 16 gage).

Piping in Solid Floors (404.8)

Piping in solid floors must be laid in channels covered so the pipe can be reached later with a minimum amount of damage to the building, and protected in an approved manner where exposed to excessive moisture or corrosive substances. As an alternative, the pipe may run in a conduit of Schedule 40 steel, wrought iron, PVC or ABS:

• One end terminating outdoors (404.8.1): the conduit extends into an occupiable portion of the building, the space between conduit and gas pipe is sealed where it terminates indoors, the conduit extends not less than 2 inches beyond the point the pipe emerges from the floor and not less than 4 inches outside the building, and it is vented above grade to the outdoors and installed to keep out water and insects.
• Both ends terminating indoors (404.8.2): the conduit originates and terminates in accessible portions of the building and shall not be sealed, again extending at least 2 inches beyond the point the pipe leaves the floor.

Outdoors, Underground and Through the Foundation

Foundation walls (404.6). Gas piping shall not penetrate a building foundation wall at any point below grade. It must enter and exit the building above grade, and the annular space between the pipe and the wall must be sealed. Where a sleeve is used, seal both the pipe-to-sleeve and sleeve-to-wall annular spaces.

Beneath buildings (404.14). Underground piping beneath a building is prohibited unless it is encased in a conduit of wrought iron, plastic pipe, steel pipe, a piping or encasement system listed for installation beneath buildings, or other approved conduit designed to withstand the superimposed loads. That conduit must be corrosion-protected per 404.11 and vented in the same one-end-outdoors / both-ends-indoors pattern used for solid floors.

Corrosion (404.10, 404.11). Zinc coating is expressly not adequate protection for underground gas piping (404.11.1); underground pipe must instead be corrosion-resistant material, factory-coated with an electrically insulating coating, or cathodically protected under an approved monitoring program (404.11.2). Dissimilar metals joined underground require an insulating coupling or fitting (404.11.3); uncoated threaded or socket-welded joints may not be used in contact with soil (404.11.5); and metallic piping carrying gas from an LP-gas storage container requires an approved dielectric fitting installed above ground, outdoors (404.10).

Trenches (404.13). The trench is graded so that the pipe has a firm, substantially continuous bearing on the bottom — no point loading on rock or backfill lumps.