Whose Job Is It to Bond Corrugated Stainless Steel Tubing (CSST)?

Oct. 22, 2012
Safety campaign encourages electrical contractors to take over bonding for CSST gas piping systems

All gas piping materials, equipment, and systems are prone to damage from lightning strikes — though this is a rare occurrence. However, because of its thinner wall, yellow-jacketed corrugated stainless steel tubing (CSST) is more susceptible to damage from direct and indirect strikes. The damage consists of an arc-induced perforation through the tubing wall created from a voltage imbalance between the CSST and another electrically conductive system in close proximity. Fires often occur with this type of damage and have resulted in partial or total losses of property (see SIDEBAR Legal Action Against CSST below).

This summer, the National Association of State Fire Marshals (NASFM), Cheyenne, Wyo., and Washington, D.C., launched a nationwide safety campaign to bring awareness to the importance of proper bonding of yellow-jacketed CSST for gas piping systems that supply natural gas or propane to furnaces, water heaters, and other gas appliances in residential applications. See more information on the campaign at

Using a 6 AWG copper wire for direct bonding of piping systems to the grounding electrode system allows these systems to be energized at (or near) the same rate as the electrical system and in unison with the voltage wave caused or induced by a direct or indirect lightning strike, according to NASFM, which bases this on evidence from electrical experts, NFPA 780 LPS bonding requirements, NFPA-SEFTIM report on validation of bonding methods, and electrical codes of other countries.While bonding the system doesn’t completely eliminate the potential for damage, according to these sources, it reduces the likelihood of this electrical surge.

The NASFM initiative was welcomed by lawmakers. On the heels of the campaign’s launch, the U.S. Senate unanimously passed a bipartisan resolution — S.RES.483 — praising NASFM’s initiative and urging “further educational efforts ... on the need to properly bond yellow CSST retroactively and moving forward in houses that contain the product.” A companion resolution — H.RES.638 — was then introduced in the House of Representatives by Congressmen Robert Dold (R-Ill.) and Ruben Hinojosa (D-Texas).

CSST was first approved for installation as an alternative to standard threaded black-iron gas piping in the United States by NFPA 54, the National Fuel Gas Code, in 1988. However, it didn’t include a direct bonding requirement for CSST until 2009, following a move prompted by a lawsuit settlement by CSST manufacturers to include bonding requirements in their installation specification in August 2006. Therefore, much of the 800 million feet of the yellow-jacketed flexible metal gas tubing installed in more than six million homes remains in need of a bonding retrofit.

With grave safety concerns, such as the threat of fire due to a surge from a lightning strike, home inspectors won’t allow these systems to be “grandfathered in.” As a result, the purpose of the NASFM safety campaign is to bring awareness to homeowners whose CSST gas delivery systems were installed before the 2006 manufacturer bonding requirement. “We have the opportunity to enhance safety by raising awareness of a risk that can be minimized,” said Jim Narva, NASFM executive director, in a press release accompanying the campaign’s launch. “This is an important public safety initiative that NASFM fully supports in conjunction with key stakeholders.”

Codes in conflict

In most U.S. jurisdictions, bonding is considered electrical work. In the National Electrical Code (NEC), Sec. 250.104(B) covers the requirements for bonding various metal piping systems, including gas piping systems, other than water piping systems. “Part V of Art. 250 in the National Electrical Code (NEC) NFPA 70 provides the minimum requirements for bonding other metal piping systems (including metal gas piping),”  Michael J. Johnston, executive director standards and safety for the National Electrical Contractors Association (NECA) and chair of the NEC Code-Making Panel 5, writes to a member of his organization. “Metal gas piping systems fall under the category of ‘other metal piping’ in the Code, and those bonding rules are provided in Section 250.104(B).”

According to Johnston, the rule calls for a bonding jumper to be connected between the metal gas piping and the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor (if it is of sufficient size), or to one or more grounding electrodes of the grounding electrode system. The connection points — points of attachment — of the bonding jumper are required to be accessible. This Code rule also indicates the minimum size for the bonding jumper generally has to be sized using Table 250.122, based on the rating of the circuit likely to energize the piping system. These circuits are generally considered as those that supply gas-fired equipment. At a minimum, the size of the bonding jumper should be not less than size of the equipment grounding conductor of the circuit supplying the equipment. The overcurrent device for the circuit determines the minimum size. One could install larger bonding jumpers and exceed the minimum. This is often specified in the plans for larger construction projects. Still, itis wise to verify with the local inspection authority how they approach sizing metal gas piping system bonding jumpers, which could be different than the NEC minimums, advises Johnston.

Despite their proficiency in bonding work, many electrical contractors are reluctant to perform bonding services on CSST systems. They cite issues regarding liability and contract restrictions. Additionally, some electrical contractors have not been aware of the issue. Until a home inspector showed a section of unbounded yellow CSST to Robert Monk, owner of Robert Monk Electric, a Philadelphia-based electrical contractor, he didn’t know the problem existed. “Until it was brought to my attention by that home inspector a few years ago, I didn’t know it was something that needed to be done,” he says.

Aside from surge protectors and the bonding of other metallic structures in the home, such as water pipes, Monk doesn’t regularly offer the installation of any additional lightning protection devices.

In their history of use in the United States, CSST systems have been installed by mechanical contractors, usually HVAC or plumbing contractors, and not included in the electrical contract. The tubing is installed using special fittings and cutting tools developed and approved by the manufacturers, which specifically gear their training toward these trades, which may also hold a limited electrical license. Striker plates must be installed where the gas lines penetrate wall studs to protect lines from puncture during drywall installation similar to the ones installed over water lines. As long as the  connection to the grounding electrode system is outside the service enclosure, these mechanical contractors may install the bonding clamp and conductor when permitted by the local authority. The CSST installer is ultimately responsible to ensure that the bonding is installed in accordance with local practices and code.

CSST installation and bonding is covered by the National Fuel Gas Code, which requires it to be listed to meet the performance, installation, and construction criteria in ANSILC 1/CSA 6.26. The 2009 editions of the International Fuel Gas Code (IFGC) and the Uniform Plumbing Code (UPC) also include bonding requirements for CSST. Proposals to include specific bonding requirements for CSST gas piping systems in the 2011 NEC were rejected by NEC Code-Making Panel 5 on the grounds that lightning protection for gas piping systems is beyond the scope of the NEC. “The mitigation of the effects of lightning is a design option,” reads the rejection. “The purpose of the NEC is the practical safeguarding of persons and property from hazards arising from the use of electricity.

“The problem is not all CSST products require any bonding beyond the minimum required in the NEC 2008,” explains Johnston, who says the NEC includes rules to protect the piping system from being energized by the electrical system in the building.

Metal gas piping systems are required to be bonded where likely to be energized so that any imposing circuit cannot energize the piping system. The bonding required by 250.104(B) also results in the potential of metal gas piping being at or near the potential of ground (the earth). “The NEC rules are generally not intended to provide assured and complete protection against lightning events,” he continues. “NFPA 54, on the other hand, includes rules that address safe gas piping system installations and now includes requirements that attempt to protect specific piping systems, such as CSST, that are known to be vulnerable to the effects of lightning.”

The bonding requirements listed in NFPA 54 do not conflict with the NEC requirements in Sec. 250.104(B). However, it does mandate that installers follow manufacturer-provided instructions for installation. In some cases, these specifications contain bonding requirements that are more restrictive than the NEC rules. “This could be where some of the inconsistencies and confusion lie,” says Johnston. “Some jurisdictions have been convinced that they need to change their local codes or add a new amendment to their current local rules that parallel the CSST manufacturer’s instructions.”

Adding to the confusion, some jurisdictions that adopt and enforce the NEC do not adopt and enforce the 2009 NFPA 54, IFGC, or UPC. Furthermore, NFPA 54 requires installers also follow all regulations from the applicable local gas supplier. “The impact on electrical contractors has been increased inconsistency and confusion regarding bonding requirements for metal gas piping systems, specifically those systems that incorporate CSST,” concludes Johnston.

Pressure or opportunity?

Until the NEC includes a provision for the bonding of yellow-jacketed CSST gas delivery systems, electricians will be reluctant to perform the service, and the burden of following the specifications will remain with the installer. Furthermore, the question of who installs the bonding clamp/conductor depends on several factors including the stage of construction — new verses retrofit, local licensing requirements for trades, local plumbing and electrical codes in effect, and opinion/ruling of local building officials.

“Electricians already bond the copper water pipe and the structural steel exactly the same way we recommend bonding the corrugated tubing,” says Robert Torbin, director of codes and standards for Exton, Pa.-based flexible metal hose manufacturer OmegaFlex. “From a technical point of view, the NFPA 54 code does not require some special type of bonding. The goal is to bond in what the electrical code refers to as an equipotential state, where everything is bonded together in a similar fashion with a No. 6 copper wire back to the grounding electrode systems. But here we are with the NEC essentially not addressing and not requiring this particular type of bonding.”

According to Torbin, the corrugated tubing industry would prefer electrical contractors take over the job of bonding. “Bonding is considered electrical work,” he says.

The industry isn’t alone in that desire. Through its CSST bonding awareness campaign, NASFM alerts property owners to enlist a licensed electrical contractor to make the correct determination on proper bonding of CSST systems. As a result of this action, with the support of their states’ fire marshals, Iowa’s Department of Public Safety issued an electrician advisory, and Oklahoma instituted a home inspector’s rule based on the campaign’s guidelines for electricians.

“This is an opportunity for electrical contractors,” says Torbin, who urges them to think of the NASFM campaign as basically an open bid to the electrical community, particularly with retrofit projects in certain areas of the country that experience more lightning density (see Map). “There are millions of homes in the United States that have the yellow CSST that was installed before the year 2007,” says Torbin. “According to NASFM, many of these homes should be inspected, and, if necessary, upgraded to current requirements.”

On new construction, Torbin advises electrical contractors to include the CSST bonding in their bids. “If there’s CSST yellow jacket in there, they should be including the extra cost in their bid so that they get the extra work,” he says. “From a revenue point of view, it’s easy money because it’s well-defined. It’s a requirement within the jurisdiction.”

For any electrical contractors still confused as to the specifics of the bonding procedure, both NASFM and manufacturers offer assistance. The manufacturers have detailed design and installation guides, which include instructions on bonding of CSST, free for downloading. In addition, the corrugated tubing industry offers free training.

“Electrical contractors could certainly attend the same classes the plumbers are attending,” says Torbin. “It’s an opportunity for them, and they shouldn’t be running away from it.”   

SIDEBAR: Legal Action Against CSST

According to the National Fire Protection Association (NFPA), there are, on average, 4,400 lightning fires every year to residential buildings. About 160 of those fires involve gas piping systems, including both rigid and flexible gas piping.

• A class-action lawsuit filed in Arkansas against four manufacturers of CSST claimed that if homeowners had a lightning strike to their house that contained yellow-jacketed gas tubing, the lightning could cause a fire — and requested that the court order all CSST be removed from every house in the United States because it posed an unreasonable risk of fire from lightning strikes. In 2006, the parties reached a settlement that was worth up to about $29 million, according to a copy of the settlement agreement.

• Last year, a jury found one brand of CSST to be a defective product and imposed strict liability against that manufacturer, awarding  100% recovery of both the subrogated and uninsured losses for a total judgment that will exceed $1 million. The jury found that the manufacturer was not negligent in the design of the product. The case involved a CSST line that was installed in 1998 and failed from the effects of indirect lightning in June 2007. The case is currently under appeal.

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