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.
Flexible Appliance Connector (FAC) OR CSST Gas Line
Lots of folks (especially new home inspectors and real estate agents) get confused 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.
What does Electrical Grounding and Bonding Mean?
NOW THAT YOU CAN SPOT THE DIFFERENCE BETWEEN CSST AND GAS APPLIANCE CONNECTORS LIKE A PRO, LET’S TALK ABOUT THE ELECTRICAL GROUNDING & BONDING OF THESE GAS SYSTEMS.
What does any of this have to do with CSST Gas Tubing?
LET US PUT IT ALL TOGETHER AND I’LL EXPLAIN BONDING OF THE CSST GAS LINE.
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.
Bonding 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 Underwriters 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.
What about the black CSST?
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.
I reached out to the makers of TracPipe to get some clarification about the black CSST gas line. They were very responsive and actually called me back the next day after I emailed them. I talked to a very nice guy named Joe (sorry I did not get his last name.)
Joe and I spoke about the bonding requirements for black CSST. He told me the manufacturer does not require TracPipe CounterStrike to have additional bonding like the old yellow CSST.
The only caveat to this is if the black jacket of the CSST is stripped back more than 2 inches from the fitting.
Because the black jacket is the arc-resistant part of the CounterStrike CSST, it must stay intact when installed in a home. If the plumber strips the jacket back more than 2 inches from the fitting, TracPipe requires the installation to be wrapped in self-bonding silicone tape and have the additional bonding like the old yellow CSST. Joe said this was the ‘unofficial- official’ rule.
The idea is pretty simple. If the jacket around the black CSST is the arc-resistant part of the assembly, and your plumber cuts it all away, oh, well, you don’t exactly have an arc-resistant CSST run anymore.
Page 27 of the TracPipe CounterStrike installation guide shows on table 4-3 (see image below) that the maximum allowed exposure of the CSST without the jacket is 1-1/2 – 2 inches.
Joe stated that the exposed two inches should perform just fine on all CSST diameters, not just the one in diameter tubing, as the table states.
If you have black CSST in your home, and the jacket has been removed more than 2 in, I encourage you to reach out to TrackPipe for detailed instructions on correcting this installation.
You will likely have to bond your TracPipe CounterStrike CSST as mentioned above for the yellow version.
Wrap up Overview
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.
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.
Are appliance connectors and CSST the same thing?
No. Lots of folks (especially new home inspectors and real estate agents) get confused 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.
Does CSST need to grounded?
Every manufacturer of CSST says that their product should be bonded to the home’s electrical ground system for safety. 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 size wire should be used when bonding CSST?
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.
Where is the bonding connection made on CSST?
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.
Hi, I’m Ben, and I inspect houses. I grew up with a hammer in my hand, and have been a professional home inspector for 12 years. My blog is here for info about home inspections around the Louisville, Kentucky area, and just about anything construction-related.
Hey Ben, in the bonding section you refer the bonding clamp and say a UL rated bonding clamp must be used and then you refer to United Laboratories. UL actually stands for the Underwriters Laboratory in Northbrook, IL. They are a service that tests (to failure) every product it certifies.
Good catch Scott. Spell check must have changed it on me. Thanks!
Thank you for sharing. Your article is very comprehensive and thorough. Great job!
Thanks, Aaron.