Bonding Jumper Missing On CSST Decision Tree
Why this matters
Corrugated stainless steel tubing (CSST) gas piping is electrically conductive but has a much thinner wall than black iron. A nearby lightning strike that energizes the building's electrical or grounding system can drive enough current through CSST to pinhole the wall, ignite the gas, and burn down the house. NEC 2023 Article 250.104(B) and NFPA 54 (National Fuel Gas Code) 7.13.2 both require CSST to be directly bonded to the grounding electrode system with a #6 AWG copper conductor minimum. A missing or undersized bond is one of the most common findings during home inspections and one of the most consequential.
Symptom presentation
Discovery is usually at home inspection, panel upgrade, or a documented near-miss lightning event. Customer-reported symptoms are rare; CSST does not "behave" differently with or without the bond on normal days. The risk shows up only with a current event.
Identify CSST by appearance. Yellow plastic jacket over a corrugated stainless tube; standard brands are TracPipe (Omega Flex), CounterStrike (Omega Flex, with black jacket and arc-resistant conductive coating), Gastite (Titeflex), Wardflex, and HOME-FLEX. Black iron pipe (no yellow jacket, smooth wall) does NOT require this bonding under NEC 250.104(B) but is required to be bonded under NFPA 54 7.13.
Quick checks
Locate the CSST manifold or the point where CSST enters the building. The bond must be made to the rigid metallic gas pipe upstream of the CSST manifold per NFPA 54 7.13.2; bonding to the CSST itself is not permitted because the bond clamp can damage the thin-wall corrugated tube.
Verify the bond exists. Trace from the rigid manifold pipe to the grounding electrode conductor (GEC) or to the service-equipment ground bar with a #6 AWG copper conductor minimum. Some installs route through the panel ground bar; some go directly to the grounding electrode. Either is acceptable per NEC 250.104(B).
Read the bonding clamp listing. The clamp must be listed for the specific use; standard split-bolt connectors are not listed for bonding to gas piping. Use a UL-listed bonding clamp such as Burndy GAR, Ilsco GTL, or the OEM-supplied bonding kit from the CSST manufacturer (TracPipe AutoFlare or Gastite XR2).
Isolation tree
If no bond is present, NEC 250.104(B) requires you to install one. Pull #6 AWG bare or green-insulated copper from the rigid gas pipe manifold to the panel ground bar or the GEC. Land on a listed bonding clamp at the manifold; land on the panel ground bar with a properly sized lug.
If a bond is present but undersized (less than #6 AWG), upsize to #6. Smaller bonds are below the NEC requirement and would not carry the fault current of a lightning event without melting; the melted conductor leaves the CSST unbonded.
If the bond appears correct but lands on an isolated grounding electrode (a rod driven specifically for the gas line, not connected to the service grounding electrode system), this is a NEC 250.4(A)(5) violation. The supplemental electrode must be bonded to the main grounding electrode system. Separate ground rods that are not bonded back to the main system create the "two-ground" hazard NEC explicitly prohibits.
If the bond is correct but the home has been remodeled and the CSST routing has changed without rebonding, walk the new routing and verify it returns to a properly-bonded section of rigid pipe.
Confirming diagnosis
Read resistance between the rigid gas pipe and the panel ground bar with an ohmmeter; should be under 1 ohm. Above 5 ohms suggests a corroded clamp or a loose termination. Above 25 ohms is a non-functional bond.
For installations with CounterStrike CSST (the black-jacketed arc-resistant variant), Omega Flex's installation instructions document slightly different bonding requirements; CounterStrike has an arc-resistant outer layer that reduces lightning damage probability, but bonding is still required by code. The OEM instructions are the authoritative source.
Remediation
Install a #6 AWG copper bond from the rigid metallic gas pipe upstream of the CSST manifold to the grounding electrode system. Use a listed bonding clamp at the gas pipe. Land on the panel ground bar with a properly sized lug or splice to the existing GEC.
Document the installation with a photograph of the bond at the gas pipe, the routing of the conductor, and the termination at the panel or GEC. Many jurisdictions require this as a separate permit-and-inspect item; verify the AHJ requirements before closing the work order.
Provide the homeowner with a written statement that the bond meets NEC 250.104(B) and NFPA 54 7.13.2. This documentation matters for insurance after a lightning event.
A CSST pinhole leak from lightning current ignites with no audible warning and burns extremely hot. Multiple residential fires have been attributed to unbonded CSST; the 2010 publication of the NEC 250.104(B) requirement followed extensive litigation and code-cycle deliberation. Treat any unbonded CSST as a same-day-fix safety call regardless of the original work scope.
References
- NEC 2023 Article 250.104(B) (Other Metal Piping; CSST bonding requirement), 250.4(A)(5) (Effective Ground-Fault Current Path), 250.66 (Size of Alternating-Current Grounding Electrode Conductor)
- NFPA 54 / ANSI Z223.1 (2024) National Fuel Gas Code, Section 7.13 (Electrical Bonding and Grounding)
- IRC 2024 Section G2411.1 (Electrical Bonding of Gas Piping)
- TracPipe Design Guide DG-01 (Omega Flex CSST installation and bonding requirements)
- IAEI Magazine, multiple articles on CSST bonding and lightning damage history