Corrugated stainless steel tubing (CSST - yellow pipes pictured above) is a yellow or black jacketed flexible gas pipe used to distribute gas from a main steel gas line or from the gas source itself to the gas appliances. It is used because of its flexibility and easy installation as compared to rigid piping. If you have a gas appliance in your home and your home was built in the 90’s or later there is a good chance you have this type of piping.
CSST should not be confused with appliance connectors like the one in the photo below:
My job during a home inspection is to evaluate the condition and installation of all accessible gas piping. When it comes to CSST the best standard to judge the installation of a home’s piping is the manufacturer's specifications.
There is one very important detail that I find continually missing during a home inspection. This detail is isolated to the yellow jacketed CSST and has to do with protecting the CSST from arc damage in the event that the home takes a direct or indirect hit from lightning. Because yellow jacketed CSST is a thin walled metal, the arcing can damage the pipe, cause leaks, and fires. There have been documented fires that have resulted in arcing of CSST. In an attempt to prevent arc damage, CSST manufacturers require bonding of the piping. It is this bonding that is often found missing during a home inspection.
What are the bonding requirements?
A 6 AWG copper wire should be used as a bonding jumper from the CSST (red arrow in photo below).
The bonding jumper should be connected to the rigid gas piping before the CSST or directly to a nut of the CSST (yellow arrow in photo below).
The bonding jumper is needed no matter how small the amount of CSST is in the home.
If these details are missing, it is recommended that the CSST be evaluated by a licensed electrician and repaired as necessary.
Black Jacketed CSST
Manufactures have created another CSST that is “arc resistant.” This CSST is covered with a black jacket. Since this type of CSST is said to be “arc resistant,” manufacturers do not require a bonding jumper for it.
If you have any gas appliances in your home, you should determine if you have this yellow jacketed CSST and then determine if it has been bonded. If you don’t feel that you can successfully determine this, it would be my pleasure to assist in evaluating your gas lines. When you really want to know, give Duncan Home Inspection Services a call.