CSST stands for Corrugated Stainless Steel Tubing. It appears to be a yellow flexible tube and can be found in some homes in the attic or as a feeder tube to gas appliances. CSST is a popular product in the greater Austin TX area, since many homes here have natural gas service. Although it is materially more expensive than traditional black iron pipe, CSST is quick to install and requires less cutting, fitting and labor time. This means that CSST is often cheaper and easier to install overall than black iron pipe, so many builders opt for it.
CSST does have very specific installation requirements. One such requirement is that the tubing itself must be bonded and grounded to the home electrical system. Failure to do so can cause pin holes to form if/when lightning strikes in the area, leaking natural gas into the home and ultimately fire, injury and loss of property or life. Essentially the CSST pinhole caused by a lightning strike on an ubbonded system can become a blowtorch in your home. CSST should not be confused with the other common flex tubes used to connect the natural gas pipe to an appliance. They are two different products.
Unbonded CSST after lightning strike
CSST electrical bonding and grounding should be verified by a licensed electrician or plumber. A thorough inspection of CSST should include confirming the correct size and installation of the ground/bond wire.