Bonding CSST

Today I’ll cover the rules for CSST bonding. Nobody cares about any of this stuff until it concerns a house you own or you’re buying, and then it’s really important. If you came here looking for some easy and helpful tips for handy homeowners, please try again next week. I’ll have a blog post about fall maintenance that’s great for any homeowner. But this week, we’re diving deep into a very specific topic.

First, CSST stands for Corrugated Stainless Steel Tubing. If you own a newer home or you’ve recently added gas lines to your home, there’s a good possibility that someone used CSST. This is a relatively new, flexible gas line used all over the country. If it were water piping, it would be PEX. If it were electrical wiring, it would be Romex®. It’s easier to install than other stuff before it, and old-school home inspectors and contractors are super-suspicious and don’t trust it. The building code doesn’t have a ton of rules for CSST; they mostly say to follow the manufacturer’s instructions. Each manufacturer has a huge document telling you about all of the dos and don’ts, and I’ve found them to all be pretty similar, as they should be.

CSST needs to be bonded. The most common issue that home inspectors find with CSST is a system that hasn’t been properly bonded. Bonding the CSST means that you’re making sure it’s at the same electrical potential as everything else. If CSST is installed without being properly bonded to current standards, you have an increased risk for damage to the material from a nearby lightning strike. If CSST is damaged, it can leak gas and cause an explosion and/or a fire. To the best of my knowledge, all manufacturers of CSST began implementing specific bonding requirements around 2006. Click the image below to see a large version of the installation tag from Gastite dated August 9, 2006.

What about existing installations?  Building codes have something called ‘grandfathering’. This means that if something was installed to code, it’s still a code-compliant installation today, even if the codes have changed significantly. The nice thing about being a home inspector is that I don’t need to get hung up on code requirements. If something is deemed unsafe due to a change in accepted residential construction standards, my Standard of Practice requires me to report on it, whether it met code at the time it was installed or not.

If CSST was installed to code in 2005 and the manufacturer didn’t have any special requirements for bonding at the time it was installed, the installation still meets code today. That won’t stop me from recommending this important safety upgrade, however. I’ll still recommend having the system bonded to today’s standards. The manufacturers of CSST have changed their installation requirements because they’ve learned that the old methods weren’t good enough. There is an unacceptable risk of fire from a nearby lightning strike with older systems.

Where does CSST need to be bonded, inside or outside of the house? It’s safe to have CSST bonded either inside or outside the house. There has been some confusion on this topic because early editions of the fuel gas code were picky about this, but the current version of the code doesn’t specify. You can bond CSST inside or outside.

Not only does the newest version of the code allow CSST to be bonded anywhere, but CSST manufacturers also allow CSST to be bonded anywhere. For example, Gastite says “The bonding clamp attachment point may be at any location within the gas piping system.” 

What does proper bonding look like? There needs to be a separate bonding wire connected either to the rigid gas piping before the CSST, or directly to one of the CSST nuts. This is needed any time CSST is installed, even if it’s just a small amount. The diagram below shows an example of what this would look like when properly installed to today’s standards.

The photo below shows an example of CSST bonded at the exterior of the home, with the bonding clamp connected to the CSST nut.

The other end of that wire shown above went into the main electric panel. The video below, produced by Gastite, shows a couple of examples of properly bonded CSST.

While the old method for bonding CSST required a connection at the main electric panel, this is no longer required by the national fuel gas code. The current Fuel Gas Code requires CSST to be bonded anywhere along the electrical service grounding electrode system. That means that the bonding conductor for CSST can be connected to the metallic water piping coming into the home, a ground rod at the exterior, or anywhere else on the service grounding electrode system. This change makes it much easier to properly bond CSST. To view the current requirement, click the following link to view Section 310.2 of the 2020 Minnesota Fuel Gas Code.

What defines the grounding electrode system? Check out section 250.52 of the National Electric Code, which lists the following:

1. Metal Underground Water Pipe
2. Metal In-ground Support Structure(s)
3. Concrete-Encased Electrode
4. Ground Ring
5. Rod and Pipe Electrodes
6. Other Listed Electrodes
7. Plate Electrodes
8. Other Local Metal Underground Systems or Structures

One place that isn’t a proper bonding location is the intersystem bonding terminal, which can be found at the exterior of homes that have been built in accordance with the 2008 NEC or later. That version of the NEC was the first to require an intersystem bonding terminal for low-voltage communication equipment such as television cables, satellites, and phones.

What about the black stuff? Some manufacturers of CSST offer a product with a black outer “arc-resistant” jacket, which tells you it’s an arc-resistant product. Two examples of these products are CounterStrike® and FlashShield™. In accordance with section 310.3 of the Fuel Gas Code, you probably don’t need any special bonding if you have black CSST.

Side note: I heard a rumor that the city of Maple Grove does not allow the installation of CSST. I called their building inspections department to ask about this, and was told that they only allow the installation of arc-resistant CSST products, such as FlashShield™. The reason for this is that they’re not comfortable with the installation instructions for the other stuff, which says “Care should be taken when installing vertical runs to maintain as much separation as reasonably possible from other electrically conductive systems in the building. There is no requirement to maintain separation from other electrically conductive systems when routing FlashShield™”  

When building officials have asked the manufacturer how much distance is required, the manufacturer has left it up to the building official. Building officials aren’t in the business of testing manufacturers products for safety; that’s supposed to be the manufacturer’s job. Because the manufacturer would not give an answer to this question, the city of Maple Grove simply won’t allow this product.

How can you know if you have CSST in your home? Look for flexible tubing with a yellow or black jacket that covers the ridges. CSST either has a yellow jacket or a black jacket. This material is not to be confused with an appliance connector, which might have a yellow coating that follows the contours of the ridges. The photo below shows the two different materials.

Side note: I’ve seen this image in numerous seminars, videos, and on various websites. I’m not boosting this image from anyone, because it’s mine :-).

The bottom line is that if you have a home with CSST, you should make sure it’s properly bonded to today’s standards, regardless of whether the installation ‘met code’ when it was originally installed. Codes change for safety and performance. Also, if your electrician tells you that bonding the CSST may increase the risk of a lightning strike, or doesn’t need to be done because the old installation “meets code”, simply thank them for their time and call a different electrician.

Additional Information on CSST and bonding

• CSST Bonding from ICC – An excellent article from the International Code Council
• Basics of CSST – a brief description, a brief history, and some basic installation requirements

Also, here’s an old news clip of me talking to Kare 11 news about CSST bonding: