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Corrugated Stainless Steel Tubing (CSST) – The New Gas Line

By In CSST On April 6, 2010


Update 1/13/17: For the latest information on CSST bonding, check out my latest blog post on the topic: CSST Bonding

Several months ago I wrote a blog about how great PEX tubing is, and today I’m going to discuss the equivalent for gas piping – Corrugated Stainless Steel Tubing, which is commonly referred to as CSST.  This is a product that can be used for the distribution of natural or LP gas throughout buildings.

A very brief history of CSST

CSST was invented in 1988, and gained approval for use in all commercial and residential installations throughout the United States in 2003.  Since then, CSST has quickly gained in popularity, and is estimated to be used in more than half of all new homes built today.

CSST Installed

The main attraction to CSST is that it’s flexible and relatively easy to install when compared to standard gas piping.  The fittings for rigid gas piping need to be tediously screwed together, and the piping itself must be measured, cut, reamed, threaded, then cleaned.  With CSST, the piping just gets cut to length and a fitting attached to the end.  It’s easy to understand why it has become such a popular product.

CSST doesn’t seem to be as popular in Minnesota

Unlike many other parts of the country, Minnesota allows the use of flexible soft copper for gas piping.  The installation procedure for flexible soft copper is comparable to CSST, making it far easier to install than rigid gas piping.  For plumbers in Minnesota that have always installed soft copper and are comfortable doing it, I’m guessing there’s probably no point in changing products.  CSST is also more expensive than standard gas piping or flexible copper tubing.

Another reason that I probably don’t see as much of this material is that it’s not readily available to the handy homeowner.  While most building products can be easily purchased at any home improvement store, CSST can’t.  That’s probably a wise thing for the CSST industry, because it means there will be less improper / unskilled installations.

How to identify CSST

CSST looks similar to a gas connector, but is easily distinguished by a flexible yellow polyethylene jacket on the outside.  Gas connectors will often have a coating on the outside – not a jacket.  CSST will also be identified as such on the jacket itself.  The most common type of CSST that I see here in the Twin Cities is Gastite – in fact, that’s all I can ever recall seeing.

CSST vs Gas Connector

CSST Installation Requirements

The general rule for CSST is that it must be installed in accordance with the manufacturer’s instructions.  Because I only see Gastite CSST, I’m listing a few of their installation requirements.  Every other manufacturer has similar requirements.  These requirements come directly from Gastite’s 102 page installation manual (fun reading).

  • Tubing shall be supported in a workmanlike manner with pipe straps, bands or hangers suitable for the size and weight of the tubing, at intervals not to exceed those shown in Table 4-3.   The referenced table requires support every 4′ for 3/8″ pipe, every 6′ for 1/2″, and every 8′ for anything larger.  “J” Hooks may not be used.
  • Tubing routed on top of ceiling joists and other structural members which comply with the horizontal support spacing requirements will be considered sufficiently supported.
  • Any portions of the exposed stainless steel tubing shall be wrapped with tape or sleeved to prevent threats by acids or chloride based cleaning solutions for masonry. Self-bonding silicone tape is recommended here for durability.
  • The Gastite® Mechanical Fittings have been tested and listed per the requirements of ANSI LC-1 for concealed use.  I include this reference because I’ve heard other home inspector say that the fittings are never allowed to be concealed.  The manufacturer says they are.
  • Outdoor installations – Along side a structure – When installed along the outside of a structure (between the ground and a height of 6 ft.) in an exposed condition, the CSST shall be protected from mechanical damage inside a conduit or chase.
  • When it is necessary to install Gastite through masonry materials the tubing shall be routed through a conduit that is a ½” larger in diameter (to ease routing) than the OD of the CSST and appropriate for the application. The sleeve must maintain a continuous watertight barrier between the masonry material and the CSST, up to or past the edge of the masonry hole.
  • Where all three of the following conditions exist mechanical strike protection must be used: Concealed, Constrained, and Within three inches of a potential thread.  That means strike plates must be used.
  • For use with movable appliances, Gastite® must be rigidly terminated before the appliance connection. This means CSST is not an acceptable substitute for an appliance connector.
  • Where it is necessary to install Gastite through sheet metal enclosures (such as fireplaces) the tubing should be routed or supported to prevent physical contact with the enclosure. If direct contact cannot be avoided a rubber grommet may be used to prevent physical contact with the enclosure. Otherwise a Gastite angle stub or rigid pipe components must be used.
  • Bonding CSST Direct bonding of Gastite® CSST is required for all gas-piping systems incorporating Gastite® CSST whether or not the connected gas equipment is electrically powered.  This last item has been the topic of many blogs and articles, and is apparently one of the more important things to look for.  Gastite has a great video on their web site showing how it’s done – click here to see it.


Reuben Saltzman, Structure Tech Home Inspections – Email – Minnesota Home Inspections



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About the Author


Reuben is a second generation home inspector with a passion for his work. He grew up remodeling homes and learning about carpentry since he was old enough to hold a hammer. Reuben has worked for Structure Tech since it was purchased by Neil in 1997, and is now co-owner and President of the company.


  • Rick Albers 4 YEARS AGO

    Have a client who has used this tubing in a fireplace. The tubing comes throgh the fireplace wall. In 2 fireplaces - the yellow casing comes all the way through the wall and exposed on the interior of the fireplace along with a small portion of the metal tubing exposed. In one case - the yellow casing does not go through the entire masonry wall. The client is concerned that this may not be an acceptable application - can the masonry corrode the tubing or any other issues.

  • Chris Jirak 7 YEARS AGO

    Reuben, CSST has been used in MN for well over a decade. It was especially used in new construction out in the "burbs" for the high pressure line from the meter to the regulator by the furnace due to the lengths possible. Soft copper is still perfered for most runs in the home. But for large homes or townhomes with long runs required... CSST is prefered, because soft copper comes in rolls of 50ft and often the line required from the meter to the regulator is over that. CSST comes in rolls of 250ft and can accommodate runs up to that legth if sized right. With runs of copper over 50ft you must braze 2 lines together and then have a joint in an unaccessible location. (leak concern over long haul) The biggest concerns for CSST are that it is sized right, and properly grounded. There have been explosion issues due to lightening strikes.

  • Reuben Saltzman 7 YEARS AGO

    Good instincts Reuben. I've always thought the same thing...

  • Reuben Collins 7 YEARS AGO

    I've got some of the flexible soft copper you mention in my basement. I've always thought it looked a little bit fishy and unprofessional....