Is CSST safe for residential gas distribution?

Yes, when properly installed and bonded, CSST is a code-approved and widely used gas piping system. The primary safety concern involves lightning-induced arcing on older, uncoated CSST that was not bonded to the electrical grounding system. Arc-resistant CSST products and proper bonding address this risk.

What does bonding CSST mean and why is it required?

Bonding connects the CSST system to the building's electrical grounding system with a copper wire and clamp. This allows any lightning-induced electrical energy to travel safely to ground rather than arc through the thin tubing wall. Many jurisdictions now require bonding of all CSST installations under the gas code.

Can CSST run through exterior walls?

CSST is generally not approved for outdoor or underground burial without additional protection, and many codes prohibit running it through exterior walls exposed to weather. Check the manufacturer's listing and local code for specific requirements in your jurisdiction.

How do I identify if my CSST is bonded?

Look for a copper wire clamped to a CSST fitting that connects back to the electrical panel's grounding system. An unbonded installation will have no visible wire attached to the gas line. A licensed plumber or gas inspector can verify whether the bonding meets current code requirements.

Does CSST require a permit to install or repair?

Yes, gas line work including CSST installation and repair requires a permit in virtually every jurisdiction. Licensed plumbers or gas fitters must perform the work, and it must be inspected and pressure tested before being covered or placed back in service.

CSST (Corrugated Stainless Steel Tubing) — Code and Safety

A CSST is a flexible, corrugated stainless steel tubing system used to supply natural gas or propane from a meter or regulator to appliances throughout a building.

CSST diagram — labeled parts and installation context

What It Is

CSST stands for Corrugated Stainless Steel Tubing. It is a flexible gas piping product manufactured from thin-wall stainless steel with a corrugated profile that allows it to bend around framing, run through walls, and navigate complex routes without numerous fittings. Most CSST systems are sold in yellow, black, or orange jacketed coils in sizes ranging from 3/8 inch to 2 inches and connect to fittings and manifolds using proprietary compression or crimp connections.

CSST was introduced in the United States in the 1980s and has largely replaced black iron pipe for interior gas distribution in new residential construction. It installs faster, requires fewer joints, and handles seismic movement better than rigid pipe. A single coil can run continuously from a manifold to an appliance without intermediate connections, reducing the number of potential leak points. However, early generations of uncoated CSST were found to be vulnerable to lightning-induced electrical arcing, which can perforate the thin wall and cause gas leaks or fires.

The tubing wall thickness is typically 0.008 to 0.012 inches, substantially thinner than schedule-40 black iron pipe. This makes CSST lighter and easier to route but also means any perforation from a nail strike, arc event, or abrasion against sharp framing is a serious safety concern that demands immediate repair.

Types

Standard CSST has a stainless steel corrugated core with a polymer jacket, typically yellow. Arc-resistant or bonded CSST features a thicker jacket and an integrated bonding conductor designed to safely dissipate lightning-induced current without perforating the tubing wall. Arc-resistant products such as CounterStrike use a conductive jacket that distributes energy over a wide area rather than concentrating it at a single point.

Several manufacturers produce CSST — TracPipe, Gastite, CounterStrike, and others. Fittings and tubing from different manufacturers are generally not interchangeable, and mixing brands in a single installation violates the product listing. Manifold systems allow a single main feed to branch into multiple dedicated runs, each sized for the BTU demand of the appliance it serves.

Where It Is Used

CSST is used to distribute gas from the main supply line to individual appliances including furnaces, water heaters, ranges, dryers, fireplaces, and outdoor grills. It runs inside wall cavities, through floor joists, and along basement ceilings. It terminates at brass fittings or manifold systems that transition to appliance connectors.

In new construction, CSST is typically installed in a home-run configuration from a central manifold near the meter. Each appliance gets a dedicated line from the manifold, which simplifies sizing calculations and allows individual appliance shutoff without affecting the rest of the system. The manifold itself connects to the rigid steel or polyethylene gas service line from the utility.

How to Identify One

CSST is recognizable by its corrugated metallic surface under a colored plastic jacket, typically yellow or black. It coils flexibly and is much lighter than black iron pipe. The manufacturer and product name are often printed on the jacket at regular intervals. Fittings have a distinctive brass body with a threaded end and a compression nut that grips the corrugated tubing.

To distinguish CSST from other flexible metallic tubing in a building, look for the printed manufacturer identification and the colored jacket. A flexible gas appliance connector at the appliance end is a different product — it is shorter, typically under 6 feet, and connects the CSST or rigid piping stub-out to the appliance inlet.

Replacement

If CSST is found to be ungrounded or unbonded in an older installation, an electrician should perform proper bonding to the building grounding electrode system using a minimum 6 AWG copper conductor rather than replacing the entire system. Bonding is required by NFPA 54 and the IFGC in most jurisdictions and must be attached to a fitting, not clamped to the tubing itself.

Sections that have been mechanically damaged, kinked, or arced through must be replaced. Replacement requires shutting off the gas supply, removing the damaged run, and installing new CSST or transitioning to black iron pipe if code or access conditions favor it. All gas work must be pressure tested at the code-required test pressure, typically 3 PSI for 10 minutes on a residential system, and inspected by the authority having jurisdiction before restoring supply.