One of the most common defects I have come across lately in home inspections is ungrounded or improperly grounded Corrugated Stainless Steel Tubing Gas line (CSST). The biggest reason for this is that CCST had become very popular starting in the early 2000’s and did not become known to be a hazard if not grounded/bonded until about 2013.
Properly bonding and grounding of a CSST system may reduce the risk of damage and fire from a lightning strike. Lightning is a highly destructive force. Even a nearby lightning strike that does not strike a structure directly can cause systems in the structure to become electrically energized. Differences in potential between systems may cause damage to the CSST, including holes. Bonding and grounding reduces the risk of arcing and other related damage. While inspecting gas lines I confirm that the CSST gas system has been properly bonded to the grounding electrode system of the premises.
The gas piping system shall be considered to be direct-bonded when permanently and directly connected to one of the following:
- The electrical service equipment enclosure
- The grounded conductor at the electrical service
- The grounding electrode conductor
- One or more of the grounding electrodes used
For single and multi-family structures, a single bond connection is made downstream of the individual gas meter for each housing unit and upstream of the first CSST connection. The bonding conductor should be no smaller than a 6 AWG copper wire or equivalent, and the bonding jumper should be attached in an approved manner in accordance with NEC Article 250.70. The point of attachment for the bonding jumper must be accessible. Bonding/grounding clamps shall be installed in accordance with its listing per UL 467 and need to make metal-to-metal contact with a steel pipe component or the first CSST fitting. This bonding requirement is in addition to any other bonding requirements that are specified by local codes.
The CSST portion of the gas piping system must not be used as the point of attachment of the bonding clamp at any location along its length under any circumstances