Regarding corrugated stainless steel tubing installed underground exterior to a building

Enacted November 6, 2013

1. Introduction

The Board of State Examiners of Plumbers and Gas Fitters (“Board”) has voted to provide this interpretation to its licensees and inspectors with regard to the installation of corrugated stainless steel tubing (“CSST”) installed underground exterior to a building. Specifically, when CSST is installed underground exterior to a building, it must be protected as required by 248 CMR 5.03(6)(j). However, this section does not explicitly address how to protect CSST piping which was initially installed underground exterior to a building, but must become exposed and accessible when approaching connection with a building’s piping system.

2. Interpretation

All exposed portions of CSST piping installed outdoors, when not underground, must be protected by a metal covering.

3. Rationale

When CSST piping is installed underground outside of the building, the portion of CSST which approaches the building, by necessity, becomes above ground and is exposed. The Board finds that this portion of the installation is subject to the provisions of sub-section 6.2.1 of NFPA 54, 2002 Edition, as adopted by 248 CMR 4.03(1). This section states that

"[p]iping installed above ground shall be securely supported and located where it will be protected from physical damage. Where passing through an outside wall, the piping shall also be protected against corrosion by coating or wrapping with an inert material approved for such applications. Where piping is encased in a protective pipe sleeve, the annular space between the gas piping and the sleeve shall be sealed at the wall to prevent the entry of water, insects, or rodents."

The Board finds that to properly protect the portion of CSST which is above ground and exposed, some type of metal covering must protect the CSST, whether it completely surrounds the CSST or otherwise attaches to the building such that it covers all exposed portions of the CSST piping. The Board further notes that the use of a plastic pipe will not accomplish this requirement. Per sub-section 6.1.7.1 of NFPA 54, 2002 Edition, as adopted by 248 CMR 4.03(1), “plastic pipe shall be installed outside, underground only.” There is an exception to this rule allowing plastic piping to be used in additional circumstances when utilizing an anodeless riser, which is a steel casing with a plastic pipe inside. Accordingly, since plastic piping used in such environments would require a metallic covering, the Board would find that the use of a plastic pipe as a covering for above ground exterior CSST to be inadequate for meeting these requirements.