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Corrugated Stainless Steel Tubing (CSST)
Description and Function
Introduced in the late 1980's
Flexible tubing wrapped with PVC plastic, typically yellow in color.
Because it is flexible, it does not require a fitting at every change in direction like steel and copper pipe. That makes it fast, easier and therefore cheaper to install. Fewer fittings also means less leakage potential. (Copper tubing is flexible and has some of the same advantages as CSST.)
Houses with CSST often have a single gas manifold and several dedicated runs from the manifold to each appliance. There are often no mains and branches for example. Manifolded arrangements are sometimes called ‘Home runs’ because every pipe comes right back home to the manifold.
There are six major manufacturers of CSST – Wardflex, Parflex, Gastite, TracPipe, Pro-flex, and Diamondback.
What can go wrong?
The tubing can be damaged by lightning resulting in a gas leak. There is a class action lawsuit against manufacturers. (See www.csstsettlement.com.) Recent changes to manufacturers’ installation guidelines call for electrical bonding and grounding of the gas piping. Bonding is the joining together a parallel electrical paths so that they will have the same electrical potential as each other, reducing gthe risk of arcing and sparks. It is important to understand that this electrical potential can be zero or any voltage. A grounding system is designed to carry electrical potential to earth, reducing voltage to zero.
A bonding system is designed to prevent electricity jumping (arcing) from one metallic path or conductor to another parallel path or conductor. This is particularly important in the case of an indirect lightning strike to a building. All of the metallic systems and building become highly energized. This includes metal siding, gas piping, water piping, electrical wiring, communication and entertainment cables etc. Damage to most of these systems is manageable, but damage to gas piping can lead to a catastrophic explosion. That is why bonding of gas piping, and particularly CSST is becoming a significant issue. There is a class action lawsuit related to this product. See www.csstsettlement.com.
In a home, the electrical system is typically grounded. Other metallic systems such as gas piping are bonded to the electrical system.
It has been broadly agreed that 6 AWG (American Wire Gauge) copper wire is the appropriate bonding conductor size required to protect CSST from indirect lightning strikes. This bonding wire should run from the gas piping near the service entrance point into the home, to the grounding electrode system for the electrical system.
The 6 AWG copper wire is larger than the grounding conductor for homes with less than a 200 amp electrical service in some jurisdictions. The bonding system relies on the house grounding conductor. This means that many existing houses do not have a large enough ground wire to provide adequate bonding for CSST. For best protection, the house grounding collector of system should be 6 AWG size wire or larger. Improvements are not typically expensive.
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