Q&A / 

Flexible Gas Lines- Are You Serious?

! ! ! See Author's Notes at Bottom of the Column ! ! !

DEAR TIM: The natural gas lines that are being installed in our new home are not the heavy black iron pipe. They are a new flexible stainless steel piping system that is installed like electrical wire. What is this material? Is it safe to use? Are there advantages to using this pipe? Can you cut into the pipe at a future date to install an added gas appliance? Is there another alternative gas piping material? Betsy F., Augusta, GA

DEAR BETSY: Congratulations! You are now the proud owner of some wonderful corrugated stainless steel tubing (CSST). This material was approved for residential use in 1988 by the National Fuel Gas Code. It is an ingenious method of supplying natural gas to fireplaces, furnaces, cooktops, clothes dryers and any other gas appliance. Virtually all state and local code authorities permit its use and many contractors are finally embracing it.

Here are two short pieces of the flexible stainless-steel gas lines. You can practically tie it in a knot it is so flexible. If you have lots of pipe to run, this may be the way to go.

Here are two short pieces of the flexible stainless-steel gas lines. You can practically tie it in a knot it is so flexible. If you have lots of pipe to run, this may be the way to go.

I remember when the material was first introduced. Many of my fellow contractors who install gas lines thought it was unsafe. Their arguments never made sense to me. For as long as I have been in the home building business, we always used similar brass appliance connector tubing when gas was supplied to a clothes dryer, a cooktop, or a gas range. Hundreds of thousands of houses have these corrugated appliance connectors in service right now. They have worked swell for many years.

The CSST has many advantages. Perhaps the biggest one is labor savings. Traditional black iron pipe takes a lot of time to cut and thread. I know as I have installed thousands of linear feet of the heavy material. As you said, the new CSST is installed like electrical wire. You simply pull the material between two points and cut it to length with simple tubing cutters. Black iron pipe is the exact opposite. A typical black iron pipe installation requires a professional to precisely measure, cut, and thread the individual pieces of pipe. All of these steps are very time consuming.

When you use CSST, you can minimize potential gas leaks. A typical black iron pipe installation has many 90 degree, tee and coupling fittings. These fittings are used each time you change directions or join two pieces of straight pipe together. Each of the cast fittings can be the source of a leak. What's more, the threaded joints on both sides of the fitting can also be potential leak points. Because the CSST snakes its way around bends and obstructions as one solid piece of tubing, you only have a fitting at each end of the line. If you do have a leak, these fittings are almost always readily accessible for adjustment.

Working with CSST is not really a do-it-yourself proposition. Many of the manufacturers of this material require professional installers to take a short training course that familiarizes them with the small nuances of this unique gas piping system.

This is traditional black iron pipe.  Each end of a piece of pipe must be threaded. It is messy and hard work, but I must admit I sort of enjoy it.

This is traditional black iron pipe. Each end of a piece of pipe must be threaded. It is messy and hard work, but I must admit I sort of enjoy it.

Adding additional gas lines at a future date is not a problem if you plan for the possibility during the original installation. The CSST systems can be installed one of two ways: a series or parallel installation. The series installation resembles traditional black iron piping. A larger diameter main line CSST pipe supplies gas to smaller branch tubes that feed each appliance. This is often the easiest system to adapt at a future date. A parallel CSST system mimics an electric panel. All of the gas lines that feed each appliance start at a central distribution point. To add a line in the future you need to have an extra gas port on the manifold within the panel.

If you are not able to get CSST tubing and can't handle working with black iron pipe, consider using soft copper. It offers all of the same advantages of the CSST systems. Soft copper is approved for interior residential gas piping in many cities and towns. You don't solder it like water lines. Connections are made with common flare fittings that tighten with standard wrenches. The only specialized tool you need is a flaring tool made to fit the pipe size you are working with. If you use copper for gas lines in your home, be sure to label them so a future weekend warrior doesn't mistake them for a water line!

 


Author's Notes:

On November 8, 2005, I received the following email.

In regard  to your article on the CSST systems being installed in new homes. If you care to, read an article that was published in April of 2003 in the Dallas News regarding banning this installation in the city of Frisco, Collin County, Texas. Lightning strikes have caused numerous fires in residential homes as a result of  CSST failing. Although the manufacturer states that it is completely safe, in fact safer than ridged black pipe, it has some serious issues. I have seen three fires in our own community as a result of CSST failure. The manufacturer accepts no responsibility for improper installation, and does not provide in any great detail, of detrimental or catastrophic failure if done so. I just saw your article and thought I would provide feedback. If you have questions on the article I mentioned, you may contact the Dallas News. Thank you for your time.

Maxwell J. Brunner
Lieutenant
Menomonee Falls Fire Department
Email- maxbrunner@menomonee-falls.org

 

I responded to this very interesting email with a few thoughts of my own. My first suspicion would be that the tubing acts like a lightning rod of sorts. The thin walls of CSST might not seem to handle as much of a strike as black iron. Black iron is so much thicker that it may actually take a lightning strike better.

I suggest you look up the article in the Dallas News if you want more details.


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8 Responses to Flexible Gas Lines- Are You Serious?

  1. Lightning strikes have caused some revisions to be made to the installation instructions for CSST. Arcing between the CSST and electrical lines was found to be the cause of these fires.

    The gas line is now required to be grounded and BONDED to the electrical system. This is usually accomplished by connecting the CSST gas line to the main ground rod with ground clamps and #6 solid copper wire.

    The 2009 editions of the International Fuel Gas Code and the Uniform Plumbing Code state in Section 7.13.2: "CSST gas piping systems shall be bonded to the electrical service grounding electrode system at the point where the gas service enters the building. The bonding jumper shall not be smaller than 6 AWG copper wire or equivalent."

    When the CSST piping is installed properly there is no more danger from lightning strikes that with any other gas system. Most manufacturers supply instructions on how to properly install ground clamps.

    I just installed a furnace in my attic with CSST piping. It was a little more expensive materials wise but saved me a lot of headaches with the complex bends and turns that were required to connect the gas line. It took me approximately 2 hours to run a CSST gas line that would have probably taken a full day of cutting and threading cast iron pipe.

  2. If there is a problem with lightening strikes why don't they put a insulating type pipe at certain points to prevent the csst from being grounded making it safe from strikes. Or use pure plastic lines that are tough enough for the job. I can't believe in this modern time we only have three choices for gas lines.

  3. Tim,

    I read your article and agree. I also read the email from the fireman. Rest assured, as an electrician we are already being told of the situation and in New York State, we are now required to bond the gas lines to the main electrical grounding electrode, in order to make sure such problems don't happen or are extensively minimized.

  4. What is meant by "bonded gas line"?
    We hired a contractor to convert an attic mounted heat pump to gas. They ran CSST from the basement to the attic alongside the refrigerant lines. Very neat install. They did attach a solid copper ground wire between the gas meter and main electrical ground using wire clamps, but how can I tell if it is "bonded"?

  5. Is there a metal gasket inside the end of the flexible pipe to keep the pipe from twisting? I unscrewed the pipe and it looks like half of one fell out. Can I just replace the end with another end piece with the gasket in it?

  6. I've heard of the lightning issue and assumed there was a way to protect against it. It sounds as if that assumption was right; knock on wood. But my objection to any flexible gas lines in the walls of a house concerns what happens when someone tries to put up a big picture, shelving, framing for new partition, just about anything that would require screws or nails into the wall. Most people do this without a thought of hitting anything sensitive, and I'm aware that they hit water pipes and even cables from time to time, but the risk from hitting a gas line seems much higher. Are there any places where such lines require steel conduits when run in closed up dead space? Seems like a small price to pay for peace of mind.

    PS: Robert M. has an interesting point. I know plastic tubing (HDPE, PEX-AL-PEX, etc.) has been used underground for years. But I wonder if pure plastic would eliminate the risk for lightening strikes; there is, I believe, some water accumulation in these systems, and a resistive path could be even more dangerous than a direct short. I can imagine a pipe heating up and bursting if the right current makes its way through the moisture, thought I can't say for sure how plausible that would be. Similar questions must come up when water lines that had been used for grounding are spliced with plastic.

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