Corrugated stainless steel tubing (CSST) is tubing made of stainless steel with
corrugation
The term corrugated, describing a series of parallel ridges and furrows, may refer to the following:
Materials
* Corrugated fiberboard, also called corrugated cardboard
*Corrugated galvanised iron, a building material composed of sheets of cold- ...
on the inside or outside.
CSST is not FAC (Flexible Appliance Connector) tubing. Presently, CSST and FAC tubing both use corrugated
stainless steel
Stainless steel is an alloy of iron that is resistant to rusting and corrosion. It contains at least 11% chromium and may contain elements such as carbon, other nonmetals and metals to obtain other desired properties. Stainless steel's corros ...
tubing. In the past, FAC used corrugated
brass
Brass is an alloy of copper (Cu) and zinc (Zn), in proportions which can be varied to achieve different mechanical, electrical, and chemical properties. It is a substitutional alloy: atoms of the two constituents may replace each other with ...
tubing. However, FAC tubing is made only in lengths of 1 to 6 feet, FAC tubing is made with connectors on each end, and FAC tubing does not have a plastic sheath. On FAC tubing the corrugations are visible. CSST's plastic sheath covers its corrugations.
Variants
The most common CSST is a type of
conduit
Conduit may refer to:
Engineering systems
* Conduit (fluid conveyance), a pipe suitable for carrying either open-channel or pressurized liquids
* Electrical conduit, a protective cover, tube or piping system for electric cables
* Conduit curre ...
used for
fuel gas
Fuel gas is any one of a number of fuels that under ordinary conditions are gaseous. Most fuel gases are composed of hydrocarbons (such as methane or propane), hydrogen, carbon monoxide, or mixtures thereof. Such gases are sources energy that c ...
distribution in buildings. It has a flexible corrugated stainless steel inner layer and an outer yellow or black plastic jacket. Yellow-jacketed CSST was developed first and is the most common. It has a non-conductive plastic yellow jacket. Black-jacketed CSST is relatively new. Its black jacket is electrically conductive. Manufacturer information indicates this conductive jacket dissipates the energy of indirect lightning strikes that might otherwise pierce or damage the yellow-jacketed CSST.
A less common type of CSST does not have a plastic jacket. It is mainly used in heat exchangers.
Usage
CSST is used as an alternative to the older standard “black iron” (steel) gas pipe. The inner stainless steel layer of typical residential CSST is .2 to .3 mm thick while the wall thickness of typical residential “black iron” gas pipe is 3 to 4 mm thick. CSST is more expensive than “black iron” gas pipe. However, CSST requires fewer joints, may be safer during earthquakes, and may be easier to install.
Properties
CSST is alleged to have an increased risk for lightning related fires. Some believe that CSST is more likely to be pierced by lightning than “black iron” pipe. There are varied opinions over CSST's fire risk and it has been involved in litigation.
Installation
Buildings with CSST should be inspected by experts (licensed
plumber
A plumber is a tradesperson who specializes in installing and maintaining systems used for potable (drinking) water, and for sewage and drainage in plumbing systems. s and
electrician
An electrician is a tradesperson specializing in electrical wiring of buildings, transmission lines, stationary machines, and related equipment. Electricians may be employed in the installation of new electrical components or the maintenance ...
s) to verify proper bonding and installation. The CSST experts should be qualified to assure compliance with the requirements of the manufacturer and local codes. Be aware that most
home inspection
A home inspection is a limited, non-invasive examination of the condition of a home, often in connection with the sale of that home. Home inspections are usually conducted by a home inspector who has the training and certifications to perform such ...
s are not done by licensed plumbers and electricians. Building owners are advised to assure that their CSST system complies with their insurance company's requirements.
To reduce the possibility of CSST lightning damage: (1) Yellow-jacketed CSST should be bonded (connected to the electrical service panel's ground bus) at its entrance into a building. Many local codes require this. (2) All CSST should be installed away from metal objects such as metal duct work, metal pipes, electrical wiring, metal beams, or metal conduit.
CSST should not make contact with sharp objects or edges to reduce the possibility of leaks caused by piercing. For example, it should not be installed where things such as picture hanger nails or drywall screws might pierce it.
References
Corrugated Stainless Steel TubingNational Association of State Fire Marshalsecmweb.comBrennen Teal FoundationCSST point of viewTexas CSST safety day Governor Rick PerryNFPA{{Refend
Corrugation
Stainless steel
Tubing (material)