How To Inspect CSST

Pipe In Attic
CSST Fastened to Rafter

Corrugated Stainless Steel Tubing – CSST is flexible pipe used for gas distribution. CSST was developed in Japan in the 1980s. More than one billion feet of CSST gas piping has been installed in more than eight million homes in the U.S. since 1990.

Plumbers prefer it because it saves time during installation and remodelers love how it fits where rigid pipe cannot.

There are a few risks when using the product and each manufacturer has its own set of proprietary fittings and installation instructions.

The design, sizing, and installation of CSST are covered in NFPA 54, National Fuel Gas Code, which references ANSI/LC-1, Standard for Fuel Gas Piping Systems Using Corrugated Stainless Steel Tubing.

In the 2009 edition of the National Fuel Gas Code, sizing tables were updated and new installation practices for the electrical bonding of these systems were added.

The protection of structures and equipment from both direct and indirect lightning strikes is considered outside the scope of the various building codes, including the electrical, fuel gas, and plumbing codes. However, all gas piping materials and equipment are susceptible to damage from lightning strikes.

Based on anecdotal data gathered from plumbing contractors and forensic investigations, it is known that lightning energy will cause pipe dope to flow inside threaded pipe joints, burn perforations through CSST and flexible connectors, and result in seal failures in gas meters, regulators, and equipment controls.

CSST is more vulnerable to arcing damage than other gas piping materials because of its thinner wall thickness. Electrical safety is enhanced if all metallic piping systems, including CSST, are bonded equipotentially to the grounded electrical system.

For Builders and Homeowners: NAHB – National Association of Home Builders WHITE PAPER


The most reported CSST defect in our area is either improperly bonded or simply no bonding has been installed.

Safety is the critical factor here. It’s vitally important CSST, like other potentially conductive systems — including rigid black pipe — be properly bonded to the structure’s grounding network.

Since 2006, all U.S. CSST manufacturers have included specific bonding and grounding procedures in their installation requirements.

Watch this video for how to bond the HOME-FLEX CSST brand.

Other HOME-FLEX Links

Keep in mind, CSST fittings aren’t interchangeable so you can’t use one manufacturer’s tubing with another’s fitting.

One manufacturer’s fitting has a retainer ring secured to the tubing between a flange and nut that are tightened together to create a seal. Other manufacturers use greased split-rings that flare against the fitting or a series of gaskets and o-rings compressed against the fitting to make the seal. Michael Buchanan, director of technical services at VPC Global, said that’s why you can’t use one manufacturer’s tubing with another’s fitting.

“Every manufacturer’s tubing and fittings are designed and tested together — the standard doesn’t require or test for interpretability between manufacturers, so mixing the brands of tubing and fittings could be very dangerous,” Buchanan said.

Plumbing and Mechanical Magazine
Nice overview of how and why fittings between manufacturers won’t fit each other.





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Home Inspector Tips

Example Termination Device
  • If you decide to use a soap test use a non-corrosive leak detection liquid – not SOAP & WATER. Don’t do the old timer’s soap test on CSST. The soap will corrode the fittings.
  • When the plumber is using a Manifold – it should be rigidly fastened to the building and may be mounted in any orientation.
  • Avoid direct contact with metallic systems. Example: Don’t allow the CSST to rest against metal duct.
  • Crushed/Dented sections of CSST pipe should not exceed 1/4 of the pipe diameter.
  • Fasten the pipe every 8 feet in horizontal install and use nail guards at the top and bottom of walls. No plastic hangers or plastic snap ties.
  • Assure CSST is properly terminated at appliances using termination brackets designed for the manufacturer.

Underground Inspection Tips

  • All CSST products are UV resistant.
  • Protect the tubing along the side of a structure when installed elevation is under 6-ft.
  • Check to see that tubing is not in direct contact with the ground.
  • Check for unwrapped/exposed stainless steel and fittings – should be protected with self bonding silicone tape.
  • A crawl space and under mobile homes are considered to be outdoors.
  • Is Permitted on roof tops with proper support and elevation.

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