What is CSST Gas Line?

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.   

CSST Gas Pipe

Flexible Appliance Connector (FAC) OR CSST Gas Line

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.

CSST and Flexible Appliance Connectors

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.

Flexible Appliance Connector

CSST Gas Pipe

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.

Large Roll of CSST

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.


ANSI Z21.24


Heads up!!! Flexible appliance connectors were once made from uncoated brass as you see in the image below. They are easy to spot as they are a dull gold color. These have been deemed a safety hazard by the CPSC for leaking and should be replaced immediately. You can learn more about this by downloading the notice here. CPSC Safety Notice.

Brass Appliance Connectors

What does Electrical Grounding and Bonding Mean?


  • What is grounding?

    Geeky Technical Answer:  Modern electrical systems have 3 wires in a simple 120v circuit- like your wall switches or receptacles that you plug things into.  A black wire, a white wire, and a bare copper.  These are the hot wire (black), the neutral wire(white), and the ground wire (bare copper).  Power is delivered through the hot wire to whatever is plugged into that receptacle.  That device completes the circuit and the current returns back to the source (the electric panel) via the white wire.  That’s it.  Notice I didn’t use the ground wire at all in this example.  It (the ground wire) runs right along the side of the white wire and terminates back at the panel where it is connected to the white wires (neutral wires).

    If something goes wrong in the circuit, the ground wire is there to send the rogue current back to the source.  Since this path has really low resistance, it causes the amperage to rise in the circuit, and the breaker to trip.  Once the breaker trips, that is called “clearing the fault” and you know something is wrong by the loss of power.

    Simple Answer

    When it comes to your home’s electrical system- the “ground” of this system is your plan B in case something goes wrong.  During everyday life, the ground wire isn’t doing anything.  It is kicked back, watching Netflix, waiting to be called into action.  It’s when things go wrong the ground wire steps up and becomes the hero.  If you get a surge in the power coming into your home, or a critter chews up a wire, it will send the power back to the source (the electric panel) so the breaker can trip.  This stops the danger of the situation and lets you know something is wrong.

  • What is bonding?

    Geeky Technical Answer:  Bonding is when multiple metal parts of a building that could carry electrical current (usually wires, or a wire and a metal pipe) are connected together- typically with jumper wires.  When this connection is made, each conductor (wires, metal pipes, etc) will rest at the same electrical potential– that is a fancy way of saying everything is even and nothing has a higher or lower electrical charge.  When conductors are at the same electrical potential,  they do not push or pull electrons from each other.  If you were to introduce electrical current on one of the wires, the bonding will spread things out and keep the voltage from wanting to arc (or jump) from one conductor to another.

    Simple Answer

    BONDING IS when ALL METAL PARTS OF A BUILDING are connected together like they are HOLDING HANDS.  Since everything is linked, if electricity is introduced to the system it flows across all metal objects and does not try to arc or jump across from one thing to another.

  • Transient Arcing

    When lightning strikes the ground, it releases an extremely high voltage electrical spike that pushes induced electrons in every direction.  If this event takes place close enough to your house, it can enter the structure via any available path.  This movement of electrons can cause arcing between the building materials that can carry electrical current.

    Simple Answer

    Transient arcing is lightening or electricity jumping between all the metal components inside your home.  This normally occurs during a power surge or lightning strike.

What does any of this have to do with CSST Gas Tubing?


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.


How to properly bond CSST gas lines

Bonding is simple, but there are a few rules that must be followed.

  • A UL rated bonding clamp must be used

    A United Laboratories listed bonding clamp 467 should be used to make the electrical connection to the CSST gas line.  Here is one for sale at Home Depot for a few bucks. Bonding Clamp.  These clamps make a solid connection point to the CSST pipe and have a hole and set screw for the wire.  And no, you can’t just wrap the wire around the pipe a few times like I’ve had people ask.  It’s $8 people…


  • A certain wire size must be used

    The wire used to create the bond between your CSST gas line and the electrical system must be a heavy gauge 6-AWG copper minimum size.  You can go bigger, but not smaller.

  • The connection to the gas line must be made at a specific spot

    The connection point made to the gas distribution system should be downstream from the gas meter or propane regulator.  Ideally, you want to put the bonding clamp in a spot where the wire will be as short as possible back to the electric panel.   You don’t want the current to have to ride 3 miles of wire before it reaches the bonding point at the panel.

    You also need to make sure the clamp is not placed on the actually CSST tubing itself like the photo below.  This is a no-no.  The clamp should go on the nut of the CSST, or the black iron pipe of the gas system as it enters the home.  You run the risk of crushing or damaging the CSST tubing when you place the clamp on it and that is a bad thing. CSST-bonding-clamp-placement

What about the black stuff?

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.


Wrap up Overview


It is vital to understand that none of this has anything to do with lightning protection for you or your home. If your house gets hit by a direct lightning strike, you replace whatever it destroys, and bury anyone who dies. No grounding or bonding will protect you from 3,000,000 volts. If you want to learn more about Lightning Protection for your home, you’ll want to research the NFPA 780 standards.

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.

The ICC (International Code Council) released this document a few years ago that is a great overview of how to properly bond CSST in your home.  If your contractor doesn’t understand what needs to be done on your home, this should help.

I also found this sad story from NBC 5 News in Texas on a house fire that killed a man from suspected CSST failure.

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