Corrugated stainless steel tubing (CSST) is a type of flexible piping used in the installation of natural gas and propane supply lines in residential and commercial buildings. CSST is a more flexible and easier-to-install alternative to traditional rigid steel or black iron pipes. It is often coated with a yellow or black exterior for identification and safety purposes. This piping is a thin-walled flexible tubing that is protected with a yellow or black protective sleeve.
The protective sleeve acts as a protective barrier to the thin metal wall of the pipe. This protective sleeve should be intact throughout the length of the pipe to ensure adequate protection and safety. When installing this tubing, the installation instructions state that the protective sleeve should only be cut back the distance of the utilized connection fitting. This length is typically two valleys, but some fittings require a distance of three valleys. Once the fitting is fully installed, the protective sleeve should terminate at the closest ridge to the connection fitting. It should be noted that various manufacturers and local codes dictate various installation instructions. All installations should be complete following these guidelines.
CSST is rated to pass through walls as long as proper protective measures and fittings have been applied. CSST can pass through walls without any additional protective fittings, so long as the installed protective sleeve is intact. If the CSST is oriented through masonry, metal, or other potential damaging material, a rigid protective sleeve should be utilized throughout the length of this transition. Due to the thin walls of the CSST, all protective measures must be practiced to prevent physical damage to the metal tubing. Damaged CSST in the form of pinholes or cracks in the pipe can lead to gas leaks. This is a significant fire and safety hazard.
It is not uncommon to see the protective sleeve at CSST cut back too far from poor installation. Additionally, protective sleeves can become damaged from physical contact with other adjacent building materials. These sections of damaged protective sleeves and exposed metal tubing should be repaired by a licensed and qualified plumbing contractor. If the pipe is damaged beyond repair, as determined by a licensed and qualified plumbing contractor, the section of CSST should be replaced with new tubing. If the protective sleeve is removed too far or has been damaged, but the metal tubing is intact, the section of missing or damaged protective sleeve can be repaired. Each manufacturer has specific detailed methods on how to repair damaged protective sleeves at CSST and these specific guidelines should be the guidelines utilized when repairing sections of CSST. Most manufacturers allow for small repairs at the protective sleeves utilizing a specific and often proprietary type of self sealing silicone tape.
Self sealing silicone tape comes in various lengths and widths. It should be applied to all exposed metal sections of the CSST. The tape has large amounts of silicone that acts as the adhesive as well as a means of sealing any potential damage at the metal tubing. It should be noted that this tape is not intended to repair damaged or cracked CSST but is intended to repair the damaged protective sleeve at the CSST. Due to the importance of the condition of gas piping, all evaluations and repairs at the rigid and flexible gas lines should be completed by a qualified and licensed plumbing contractor.
Corrugated stainless steel tubing is a convenient and safe product when installed correctly by following the guidelines dictated in the manufacturer’s installation instructions. Ensuring that this gas piping is properly protected from physical damage can prevent potential gas leaks and help mitigate potential fire and safety hazards.