IRC G2411 CSST Bonding: Protecting Gas Lines from Lightning

Corrugated stainless steel tubing, or CSST, is the flexible gas line that installs faster than rigid black iron and shows up in most new Arizona homes. It carries one safety rule that rigid pipe does not, and in a state with violent summer lightning, that rule earns its keep. Section G2411 of the International Residential Code spells it out.

What Section G2411 requires

Section G2411 works in two layers. Every gas piping system, whatever the material, has to be electrically bonded so a fault current has a safe path back to ground. Systems built with CSST then get a second, dedicated bond straight to the home's grounding electrode system.

The bonding jumper shall not be smaller than 6 AWG copper wire or equivalent.

That single copper jumper is the whole safeguard. It ties the gas tubing to the same ground as the electrical service, so the two metal systems sit at the same voltage when a surge hits.

Why bonding CSST stops a fire

The danger here is not the gas catching a spark at the burner. It is lightning. A strike on or near the house dumps a huge voltage onto every metal system inside. If the CSST is not bonded, that energy can jump, or arc, from a nearby metal object to the thin wall of the tubing, burn a pinhole, and ignite the gas inside. Bonding gives the surge an easier route to ground, so it drains away instead of punching through the tubing. That is why the rule reads as a lightning rule, and why Arizona's monsoon storms turn it from paperwork into real protection.

How the bond is actually installed

The details are specific, and an inspector checks them. The jumper is a solid or stranded copper wire, at least 6 AWG, run as short as practical and no longer than 75 feet measured along the wire. It clamps to the gas system downstream of the meter, or downstream of the propane second-stage regulator, on a length of rigid pipe, a steel fitting, a manifold, or a brass CSST fitting. It never clamps to the corrugated tubing itself. The far end connects to the grounding electrode system: a ground electrode, the grounding electrode conductor, or the service enclosure, using a clamp listed for the job. One clamp bonds the entire system, no matter how many runs branch off it.

The black-jacket exception

Newer arc-resistant CSST, sold with a black jacket marked AR, is built to shrug off a strike on its own and does not need the extra bonding jumper (Section G2411.3). The common yellow CSST does need it. If any yellow tubing is in the system, or if a black-jacket system is later modified with a piece of yellow tubing, the whole system gets bonded the standard way. When there is any doubt, a careful builder bonds it.

Propane versus natural gas in Arizona

Both fuels follow the same bonding rule, but the attachment point differs. On natural gas, the jumper connects downstream of the utility meter. On propane, common on rural lots around Rio Verde and other spots outside city gas service, it connects downstream of the tank's second-stage regulator. For example, on a propane-fed home in Rio Verde, the electrician clamps a 6 AWG copper jumper to the steel pipe just past the second-stage regulator and runs it to the ground at the electrical service, a path kept well under the 75-foot limit. The lightning risk is the same for both fuels, so the bond is required either way.

Which code edition your city uses

The CSST bonding language did not change between the 2018 and 2021 IRC. The ICC reaffirmed it without modification for the 2021 edition. What can differ is a local amendment, since a handful of AHJs add their own wrinkles. Check your city's adopted edition, and any amendments, in the building code editions by city reference.

Who has to coordinate on this

One jumper, two trades. The plumber sets the gas piping and the electrician lands the bond, which is exactly why the connection gets missed on a job where nobody owns it. Put it on somebody's scope in writing. The rest of the gas install is covered under fuel gas piping, and the system has to pass the gas pressure test before it goes into service. The ground the tubing bonds to is the same one established for your electrical service. Chapter 24 of the 2021 IRC carries the bonding text.