CSST is a flexible gas line material that has been used in millions of homes across the United States and the world.  CSST is short for Corrugated Stainless Steel Tubing.  It was invented in the 1980’s in Japan.  The reason for the development of CSST was to improve the safety of gas line systems in buildings during earthquakes.  The idea was that if a building started to move during an earthquake, it should have a gas line that moves with it.   One of the biggest dangers of buildings during earthquakes is gas leaks that occur after the shaking has stopped.

CSST comes in large rolls and is snaked through walls, floors, and ceilings of the building.  It is used frequently in construction in lieu of black iron pipe today, which is the traditional material used for gas distribution (both natural gas and propane).   If your home is newer (say built in the past 20 years or so) there is a very good chance you have CSST installed as part of your gas distribution system.

What we are learning now is that installations of CSST gas pipe need an additional bonding point to the home’s system grounding for fire safety.  There have been house fires blamed on faulty CSST installation without this bonding.  CSST is flexible so it can be snaked through the structure.  Because it is flexible, the walls of the pipe have to be thin.  When certain conditions of an electrical storm are present around/in the home, the CSST can fail, create a gas leak, and start a fire.

Throughout this post, I’ll explain how to verify if you have CSST in your home, what bonding means from a technical standpoint, and how the bonding should be installed.  Keep in mind that this job requires you to run wires inside the electrical panel of the home so you’ll want to let the pros handle this one.  This is not a DIY repair.   

Lots of folks (especially new home inspectors and real estate agents) get confused with when they look at a flexible appliance connector or FAC and think it is CSST.  To the untrained eye, they do look a lot alike.  They are similar in the fact that both are made from flexible stainless steel, and both are typically yellow in color. Yellow is the universal color for anything gas related in a home.

Let’s go over the main differences in the two products, and then we’ll cover bonding (what that is and why it is important) and the special rules that only apply to CSST style tubing.

1.  Flexible Appliance Connectors (FACs) are short pre-made store-bought pieces.  Usually no more than a few feet long.  They are designed to connect an appliance to the gas distribution system of the building, which can be made up from black iron pipe or CSST.  CSST comes in rolls as long as a few hundred feet.  It is snaked through the building as part of the distribution system and the runs are cut and put together on the job site.

2. Most FACs are painted yellow from the factory.  The painted FAC has very pronounced ribs you can see and feel on the tubing.  CSST has the same style body, but you can barely make this out because of the thick heat-shrink style jacket that is covering the tubing.  The ribs on CSST gas lines are not as pronounced as they are on FACs.

3. FACs are usually smaller in size (diameter) than CSST.  Most of the FACs I see are 3/8″ to 5/8″.  Most of the CSST runs are 1/2″, 3/4″ and even up to 1″.  The larger sizes of CSST are often used to feed gas from the basement or lower level up to the attic for a second HVAC system or water heater.

4. FACs will come with a data tag hanging on them, unless the installer tears it off.  All FACs are made under the ANSI Z21.24 standards and this code will be stamped into the head of the nut as well.  Since CSST is a custom install cut from long rolls and made on site, there is no store bought tag on the line or ANSI rating on the nuts.

Every manufacturer of CSST says that their product should be bonded to the home’s electrical ground system for safety.  Here is a link to some instructions released by  HomeFlex and TracPipe.  I’m sure there are many other manufacturers but these are the big two I see in my area.  From the research I did, it seems that bonding has been required since around 2006, which means that there are lots of homes throughout the world that have no bonding installed on the CSST.  In fact, in my home inspections here in Louisville, KY, I can’t recall ever seeing it done, and I see the product almost daily.

The idea is fairly simple.  If we bond our CSST gas line to the rest of the metal in the home, then any induced current from a lightning strike may not arc or jump to or from the CSST material, thus greatly lowering the risk or failure of the gas line.   What you really need to pay attention to is the keyword “may.”  The truth is you can’t know what will happen, as lightning does what it wants.  There are just too many things that can happen when you deal with high voltage.

It’s worth noting that there is a newer version of  CSST that has a black jacket on it that has been available for the past few years.  One popular brand that is sold is known as TracPipe Counter-Strike.  An excerpt from their website states:

TracPipe^® CounterStrike^® is a patented CSST innovation based on our existing TracPipe^® CSST product, but that is engineered to significantly decrease the potential for lightning induced damage to fuel gas piping systems. TracPipe^® CounterStrike^®has been designed with a proprietary jacket material in place of the standard yellow jacket. This black jacket has energy dissipating properties that will help protect the TracPipe^® CounterStrike^® stainless steel pressure liner as well as other fuel gas system components if the TracPipe^® CounterStrike^® becomes energized due to lightning.

TracPipe^® CounterStrike^® is designed to withstand significantly higher levels of lightning energy when compared to conventional TracPipe^® with the yellow jacket. TracPipe^® CounterStrike^® has been shown to be up to 400 times more resistant to the damaging effects of electrical energy than conventional CSST.

No product, including the improved TracPipe^® CounterStrike^® is immune to the damage caused by a direct lightning strike. Refer to NFPA 780 for lightning protection systems for buildings and building systems.

Does this mean the black stuff doesn’t have the same problems as the yellow?   I don’t know.  Maybe.  I’ve not heard of any failures from the black stuff, but it’s still early.  Would it still be a good idea to bond your CSST even if you have the black stuff?  Probably.  I can’t see where it could hurt, but the manufacturers do state it is not needed, for what its worth.

So. We bond the CSST to the ground buss in the electric panel and hope for the best.  All of this is worst case scenario, and most of you will never have any trouble out of your CSST.  Just know that if you do have a problem, it can be catastrophic.  I encourage you to check your home or have a pro come help check your home to see if you have CSST installed, and double check to see that the bonding was properly installed.  Chances are that it was not done at all, and you need to rectify that.