Illinois Flexible Gas Line Code: CSST Bonding, Permits, and Testing

The Illinois flexible gas line code is not a single standalone rulebook. Illinois adopts the federal pipeline safety regulations at 49 CFR Parts 191, 192, 193, and 199 as its minimum safety standard through Title 83, Part 590 of the Illinois Administrative Code, layers on the Illinois Gas Pipeline Safety Act at 220 ILCS 20, and defers to nationally recognized product and installation standards, most importantly ANSI LC 1/CSA 6.26 for corrugated stainless steel tubing (CSST) and NFPA 54 for bonding.¹² Permits are pulled locally, and the Illinois Commerce Commission (ICC) enforces the state framework.³

Who Regulates Flexible Gas Lines in Illinois

Two layers of authority apply to any flexible gas line in the state. The ICC’s Pipeline Safety Division inspects intrastate gas pipeline facilities and enforces the state’s adopted federal safety standards under an agreement with the federal Pipeline and Hazardous Materials Safety Administration.⁴ The Gas Pipeline Safety Act at 220 ILCS 20 gives the ICC authority to adopt standards at least as strict as the federal minimums and to add state-specific requirements on top.²

Below the state layer, permits and inspections for residential and commercial gas piping work happen at the municipal level. Building departments review the planned work, verify contractor credentials, and inspect the finished job before it can be placed in service. Requirements vary from one city to the next, so the local building department is your first call on any specific installation.

Materials and Installation Standards

The technical floor for flexible gas piping in Illinois comes from 49 CFR Part 192, which is adopted through Part 590 and covers material specifications, design, construction practices, and testing.¹ Part 192 requires materials and fittings to meet published specifications from bodies like ASTM and ANSI, and it mandates excess flow valves on qualifying service lines so gas shuts off automatically if a line ruptures.⁵

For CSST specifically, the governing product standard is ANSI LC 1/CSA 6.26. It requires striker plates to protect installed tubing from puncture, caps system sizes at two inches nominal inside diameter, and prohibits direct burial underground unless the tubing runs inside an approved conduit.⁶ Copper and steel tubing used as flexible gas piping must meet their respective ASTM specifications for wall thickness, corrosion protection, and composition.⁷

Correct installation goes beyond routing tubing between two points. Fittings and connections must be compatible with the specific tubing product, and installers need to follow manufacturer instructions for support spacing so joints don’t take stress from sagging over time. Any point where a flexible line passes through a wall, floor, or other structural element needs a strike plate or sleeve, because a nail or screw driven into a future renovation is one of the most common ways a gas line gets punctured.

CSST Bonding Requirements

Bonding is where most residential CSST problems begin. The thin stainless steel wall that makes CSST flexible also makes it vulnerable to electrical arcing. When lightning strikes near a building, the surge can travel through wiring or other metal systems and jump to the gas piping. If the CSST is not bonded, that energy can burn a pinhole through the tubing wall and ignite escaping gas.

The National Fuel Gas Code (NFPA 54) requires that a gas piping system containing CSST be electrically continuous and directly bonded to the building’s electrical service grounding electrode system, or to a lightning protection grounding electrode system where one exists. The bonding jumper must be at least 6 AWG copper, and the run from the gas piping connection to the grounding electrode system cannot exceed 75 feet. The jumper attaches to a metallic pipe, pipe fitting, or CSST fitting, and any bonding device used must be listed for that purpose.

Section 250.104(B) of the National Electrical Code separately requires that metal piping systems likely to become energized, gas piping included, be bonded to the equipment grounding conductor, the service equipment enclosure, or the grounding electrode conductor. The two requirements work together. NFPA 54 sets the CSST-specific rule; the NEC covers the general electrical bonding obligation for metal piping.

Yellow-jacketed CSST installed before bonding rules were widely enforced may have no bonding at all. Having a licensed electrician verify and, if needed, add a bonding jumper is one of the cheaper safety upgrades available on an existing system.

Permits and Local Inspection

Gas piping work in Illinois requires a permit from the local building department. The application typically includes a description of the planned work and the credentials of the contractor performing it. Skipping the permit creates problems that outlast the project itself: unpermitted work is often excluded from homeowner’s insurance coverage and can derail a future sale when it surfaces during a buyer’s inspection.

Residential gas line inspections come up most often in three settings. New construction and any permitted piping work get inspected before being placed in service. Appliance installations that involve new or modified gas connections trigger the same review. And during a home sale, inspectors regularly flag visible CSST without proper bonding, outdated fittings, or other defects that a buyer’s lender or insurer may require you to correct before closing. Illinois’s Real Property Disclosure Act requires sellers to disclose known material defects, and a gas line problem you know about is one of them.

Testing and Documentation

Before a new or modified gas line goes into service, it has to be pressure tested. Standard practice is to pressurize the system with air or nitrogen to roughly 1.5 times normal operating pressure and hold it for 10 to 30 minutes. Any measurable pressure drop over the test window points to a leak that has to be located and repaired before the system can be approved.

Records matter as much as the test result. Keep the permit, the inspection sign-off, and any manufacturer documentation for fittings and tubing. If you file an insurance claim or sell the property, that paperwork closes off the most common line of dispute.

Penalties and Insurance Consequences

The Illinois Gas Pipeline Safety Act ties civil penalties to the federal maximum at 49 U.S.C. § 60122(a)(1) for each day a violation continues.⁸ Under the 2025 federal adjustment, that maximum is $272,926 per violation per day, with a cap of $2,729,245 for a related series of violations.⁹ The ICC weighs the size of the operator’s business, the seriousness of the violation, and any good-faith effort to fix the problem when setting the actual amount. The ICC can also order specific corrective work, requiring repair, replacement, or re-inspection within a stated deadline.

For a homeowner, the more likely financial hit is on the insurance side. Standard homeowner’s policies generally cover fire or explosion damage that follows a gas leak, but insurers can deny the claim if they determine the leak came from improper installation or neglected maintenance. Unpermitted work or unbonded CSST gives the insurer a clean basis to reject payment, leaving the property owner responsible for repairs and any resulting damage.

Practical Safety Steps

Code compliance is the floor. A few habits close the gap between meeting the rules and actually keeping the system safe.

Have a licensed electrician verify bonding on any existing CSST, and add a 6 AWG copper jumper if one is missing.
Use licensed contractors and pull a permit for every job. Unlicensed work voids manufacturer warranties and creates insurance exposure.
Protect flexible lines run outdoors or in crawl spaces from physical damage below six feet of elevation. Tubing should never sit directly on the ground, and exposed stainless steel benefits from a wrap of self-bonding silicone tape to prevent corrosion.
Consider excess flow valves on customer-owned piping where supply pressure allows, even beyond the situations where federal rules already require them.⁵
Keep the permit, inspection sign-off, and material documentation together with your home records.

1
Illinois General Assembly. Illinois Administrative Code Title 83 Part 590 – Minimum Safety Standards for Transportation of Gas and for Gas Pipeline Facilities
2
Illinois General Assembly. Illinois Code 220 ILCS 20/3
3
Illinois Commerce Commission. About the Pipeline Safety Program
4
Pipeline and Hazardous Materials Safety Administration. Regulatory Fact Sheet: Illinois
5
eCFR. 49 CFR 192.381 – Excess Flow Valve Performance Standards
6
ANSI Webstore. ANSI LC 1-2018/CSA 6.26-2018 – Fuel Gas Piping Systems Using Corrugated Stainless Steel Tubing
7
eCFR. 24 CFR 3280.705 – Gas Piping Systems
8
Illinois General Assembly. Illinois Code 220 ILCS 20 – Illinois Gas Pipeline Safety Act
9
Federal Register. Revisions to Civil Penalty Amounts, 2025