What is Corrugated Stainless Steel Tubing?
CSST is a flexible, stainless steel pipe used to supply natural gas and propane in residential, commercial and industrial structures. Coated with a yellow, or in some cases, a black exterior plastic coating, CSST is usually routed beneath, through and alongside floor joists in your basement or crawlspace, inside interior wall cavities, and on top of ceiling joists in attic spaces.
CSST was developed in Japan in the 1980s. It was developed as a safety improvement over rigid black iron gas pipes that often failed and started fires during earthquakes. The flexible nature of the CSST system allows it to handle seismic activity without leaking gas.
Sales of CSST in the U.S. began in 1990 with approximately 100,000 ft. sold. Use of CSST grew in the U.S. as contractors quickly discovered it could be installed in 1/3 the time of rigid black iron pipe systems. Beyond the time saved on installations, contractors and code officials appreciated the reduction of fitting joints in a flexible gas piping system. Joints are areas for concern in gas piping systems as they represent potential leak sites. Flexible CSST systems have approximately 75% fewer fitting joints than rigid black iron pipe systems.
All CSST manufacturers expressly added the bonding and grounding procedure to their installation requirements in August 2006. This improved safety installation requirement reduces the likelihood of arcing damage from an electrical surge that can potentially cause a fire.
More than one billion feet of CSST gas piping has been installed in approximately eight million homes in the U.S. since 1990.
Benefits of CSST
Installation and Safety
Like all gas piping systems, CSST must be properly installed. CSST must be installed by a qualified professional and in accordance with the Manufacturer’s Design and Installation (D&I) Guide, which now expressly includes bonding and grounding of the system. The D&I Guide specifically calls for the system to have a minimum 6-gauge bonding wire between the CSST and the building’s grounding electrode in order to reduce the chances of a natural gas leak or fire from electrical/lightning energy. Some previously installed CSST systems may not have the proper bonding for optimal safety.
Bonding and Grounding
If CSST is found after having your home inspected, it is strongly recommended that you determine if the CSST system is properly bonded and grounded. A bonding device and conductor should be installed on your natural gas system in order to reduce the chances of a natural gas leak or fire. Bonding is provided primarily to prevent a possible electric shock to people who come in contact with the gas piping and other metal objects when there is a failure in a branching circuit. Nearby lightning strikes can also result in an electrical surge and can potentially puncture a hole in the CSST due to arcing.
Since 2006, manufacturer’s instructions have required direct-bonding and grounding of yellow CSST in new installations. A bonding connection installed on a gas piping system, as with any metallic system within a house, will reduce the likelihood of electrical arcing to or from other bonded metallic systems in the structure, thus reducing the likelihood of arc induced damage.
CSST is often coated with a yellow, or in some cases, a black exterior plastic coating. CSST should NOT be confused with flexible gas appliance connectors — the product that joins a moveable appliance to your home or building’s gas supply line.
Bonding: Connecting metallic systems to establish electrical continuity and conductivity.
Grounding: Connecting to the ground or to a conductive body that extends to ground connection.