Key takeaways
- CSST is the yellow flexible gas tubing common in homes built or re-piped from the 1990s onward. It has to be electrically continuous and bonded.
- The bonding jumper cannot be smaller than 6 AWG copper, and its run between the gas piping and the grounding electrode system is limited to 75 feet.
- The hazard is lightning. An indirect strike can induce current in gas piping, and an unbonded line gives that current a reason to arc through the tubing wall.
- It is electrical work, not plumbing, which is why a home inspector defers it to an electrician.
It usually reaches us through a home inspection report. Somewhere in the electrical section there is a line about the gas piping not being bonded, a photo of yellow flexible tubing in the attic, and a recommendation to have it evaluated by a licensed electrician. The buyer reads it, cannot tell whether it is a formality or a fire hazard, and calls to find out.
It is not a formality. It is also not expensive. Here is the whole picture.
What CSST is
CSST is corrugated stainless steel tubing, and it replaced rigid black iron pipe for a lot of residential gas distribution starting in the 1990s. It is flexible, so it runs through a house the way electrical cable does instead of being assembled from threaded straight lengths and fittings. The standard product is jacketed in bright yellow, which makes it easy to identify. Later arc-resistant products use a black jacket and follow their own manufacturer requirements.
It is a good product installed correctly. The wall of the tubing is thin, though, and thin is the operative word for what follows.
The hazard is lightning, specifically
When lightning strikes near a building, it does not need to hit the structure to matter. The strike induces current in metallic systems throughout the house: the electrical wiring, the water piping, the gas piping, metal ductwork, all of it. Those systems are at different potentials for a moment, and current will attempt to equalize them by whatever path it can find.
If that path runs from an energized metallic system to unbonded gas piping across an air gap, it arcs. An arc against the thin wall of stainless tubing can perforate it. A hole in a gas line, at the exact location where an arc is occurring, is the failure mode this rule exists to prevent.
Bonding removes the reason for the arc. Tie the gas piping into the same grounding electrode system as everything else and there is no significant difference in potential to jump across.
What the code actually requires
The fuel gas code requires that a gas piping system containing one or more segments of CSST be electrically continuous and bonded to the electrical service grounding electrode system, or to the lightning protection grounding electrode system where one exists.
Two specifics matter for a homeowner reviewing work.
- The bonding jumper cannot be smaller than 6 AWG copper wire or equivalent. This is heavier than people expect for a conductor that carries no load in normal operation, and it is heavy for a reason: it is sized for a lightning event, not for a circuit.
- The length of the jumper between the connection to the gas piping and the connection to the grounding electrode system cannot exceed 75 feet, which is what drives where the connection point ends up.
The connection on the gas side lands on a rigid pipe component upstream of the CSST, typically at the manifold or the rigid pipe near the meter, using a listed clamp. It does not clamp to the corrugated tubing itself, and it does not clamp to the yellow jacket.
Why an electrician and not a plumber
Because the work is running and terminating a conductor into the electrical grounding system. The gas side is one clamp on a pipe. The rest of it is electrical: selecting the conductor, routing it, and landing it correctly at the grounding electrode system or the service equipment.
This is why Texas home inspectors report missing bonding as an electrical deficiency and defer it to an electrician. It is also why the item so often sits unresolved: the gas contractor considers it outside their scope, the buyer assumes the plumber will handle it, and nobody calls the trade that actually does it.
What it takes to correct
In most homes this is a short visit. We verify what is actually installed, since not every yellow line in an attic is CSST and not every CSST installation is unbonded, identify a suitable rigid connection point upstream of the tubing, run the conductor to the grounding electrode system, and land it. The cost is driven by the run: an attached garage with the panel on the shared wall is quick, and a two-story house with the gas manifold on the opposite corner from the service is not.
The other thing worth doing while someone is at the panel is confirming the grounding electrode system itself is intact. In older homes we find bonding jumpers that were never installed, ground rods with no connection left on them, and water pipe bonds that were cut during a re-pipe. A bonding conductor landed on a grounding system that does not go anywhere is decorative.
That verification is part of an electrical inspection, and the correction is straightforward electrical repair work quoted flat before we start.
If you are buying the house
Missing CSST bonding is one of the most common electrical items on a San Antonio inspection report on a home from the 1990s forward, and it is one of the easiest to negotiate because the scope is small and clear. Get a number for it rather than a hand wave. It belongs on the list with the other electrical items, not treated as a separate mystery.
The rest of that list is worth knowing in advance, which we covered in the electrical items that show up on a San Antonio home inspection. Whether a given correction needs a permit is addressed in electrical permits in San Antonio.
We handle bonding corrections across the metro, and they cluster in the newer housing stock where CSST is standard, from Alamo Ranch and Cibolo to Converse. Send us the page from your inspection report and we will price the fix.