Corrugated Stainless Steel Tubing or CSST for short is a newer type of gas pipe first used around 1988. It's a flexible pipe covered with a plastic sheathing and is very common to see in newer homes. To make the pipe flexible a continuous ridge was designed into the pipe. Which is how the "corrugated" made it's way into the name.
CSST is a great advancement in gas piping. Because it is flexible and available on large spools long continuous pipe runs are possible without the need for connections. Fewer connections mean less potential for leaks.
However a problem with the pipe began to show up some years after the first installations.
Because the pipe is metal it is electrically conductive. What was discovered after some years was that a lightning strike entering the home can disperse through the CSST resulting in holes in the pipe (see picture). The ridges are thought to create electrical arcs and at some point along the path burn a hole through the tubing.
A hole in a homes gas supply piping, as you can imagine, is not a good thing.
Because of this problem a class action suit was brought against 4 of the 6 manufactures of CSST alleging; "that CSST poses an unreasonable risk of fire due to lightning strikes."
The solution has been to electrical bond the CSST to ground. Or more accurately more thoroughly bond the system. Bonding of gas piping was in existence in the National Fuel Gas Code (NFGC) in 1988 (diagram).
The manufactures have now written electrically bonding the CSST into their design and installation manuals. Never the less I do not see CSST electrically bonded during an inspection.
The second to last picture is from a home built in 2005. The picture is of the main gas supply pipe entering the home. There should be a ground wire on this pipe. Additionally in some jurisdictions there should also be a bonding jumper wire at connections which are missing in the last photo.
There is still debate on the requirements of bonding CSST. As an inspector knowing the potential for a fire due to a lack of bonding on a CSST system there is no debate for me. When I find CSST in a home without bonding it is called out as defect with a recommendation to correct.
James it is important to call this out---especially areas that have a lot of lightning strikes. The CSST manufacturers merely require that the gas piping system be bonded witht he same size wire that grounds the house electrical system.
I have never heard of the joints themselves having to be bonded---just the system itself. In this area the only thing that is required for gas piping systems with CSST in them, is that the piping has to be bonded with the same size wire as the service itself---it is usually done near the meter or near the furnace and water heater---wherever there is hard-pipe. All the connections are metal to metal. I think the idea is that any big fault to ground (ie lightning strike) will follow the bigger wire----as opposed to rippling out thought the CSST.
Reuben, No I have never seen a single system bonded. Considering the push to bond has been relatively recent I am not surprised none of the systems I see lack bonding.
Charlie, The bonding clamp must be on the CSST nut, not the hard pipe. The sizing of the ground wire is still under debate, but it looks like #6 copper will become the standard. As far as a jumper that is something that I was told by a city official here in CT. It is possible that requirement is unique to his jurisdiction.
Reuben, That installation differs from the TracPipe. TracPipe installation specifies the clamp must attach to the brass nut like in the diagram above. My understanding is the six manufacturers are supposed to come up with a universal installation. We'll have to wait and see.
James - that might be something that your local jurisdiction is requiring. The installation instructions for TracPipe say it can also be "bonded to a black pipe component (pipe or fitting) located in the same electrically continuous gas piping system as the AutoFlare® fitting."
Reuben, Yep, you're right it does say or... The seminar I attended was by a local electrical inspector. He said that was where they should be (brass nut). Bottom line is this stuff has to be grounded.
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A hole in a homes gas supply piping, as you can imagine, is not a good thing.
The manufactures have now written electrically bonding the CSST into their design and installation manuals. Never the less I do not see CSST electrically bonded during an inspection.
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I found this article to be very interesting. I look forward to more from you.