This technology promises time savings and a better result, but can contractors accept it?

Corrugated Stainless Steel Tubing (CSST) was introduced to the American market in 1987, when it became listed by the American National Standards Institute (ANSI). Prior to this, CSST had been used in Japan and Europe since 1980 with excellent results. It was hailed as one of the greatest technological advances in delivering fuel gas to residential appliances. The steel tubing had several advantages over black steel pipe, which had been used for fuel gas for the past century.

One of the most dramatic benefits of the new material was the amount of installation time it could save. Even though CSST was substantially more expensive than the traditional black steel, its overall price, including labor and material costs, was cheaper than black pipe.

It also featured many benefits over the traditional method in its durability and practicality. CSST has a proven resistance to leaks - due to far fewer connections made during installation. When black pipe is installed, every time the pipe changes direction, a joint needs to be fitted and checked for leaks. CSST offers flexibility and is able to be snaked through walls and around obstacles with fittings placed only at the ends of the run. By most estimates, CSST can be installed in under 25 percent of the time it takes to install black pipe.

Many contractors have realized the benefits of using CSST. In the first 10 years of CSST's existence in the American market, sales of the material have exploded, going from 200,000 feet sold during 1988 to 1990 to more than 20 million feet sold in 1998 alone. From 1996 to 1997, sales doubled as CSST became accepted into the BOCA National Mechanical Code and the ICBO Uniform Mechanical Code.

However, the International Association of Plumbing and Mechanical Officials (IAPMO) is having difficulties deciding whether or not to accept the material and approve it in its code.

The Battle

One of the primary reasons cited by IAPMO to not certify CSST is its lack of interchangeability. There are currently six manufacturers of CSST. Each of these manufacturers designs their product so they are not interchangeable with other manufacturers' versions of CSST. Installations of CSST require someone who is officially trained by the specific manufacturer of the product.

However, according to Dan Roberts, senior applications engineer of TiteFlex Corp., manufacturers produce CSST in this manner so the company can sell the product as a system with a warranty.

"Aside from this," says Roberts, "CSST is not interchangeable, but it is inter-connectable by standard fittings. PEX tubing was also not recognized for a long time because the systems were not interchangeable, but they are inter-connectable, so eventually PEX tubing became accepted. I think the same thing will happen with CSST."

In the IAPMO Report on Proposals, which is the document that shows the actions to be taken by IAPMO, Sidney Cavanaugh, special representative for the United Association, is one of three who voted not to accept CSST. In his explanation, he cites eight reasons for his dissenting opinion. (This document is available at on pg. 50.)

One concern of Cavanaugh's is CSST's lack of resistance to punctures from nails being driven into the wall by homeowners. Roberts counters that CSST is puncture resistant because, in most cases where CSST is fed through the walls, it is hanging and is likely to move aside when a nail penetrates the wall. In places where the tubing is attached to something (therefore immobile), it is protected by hardened steel puncture plates that deflect nails and are puncture proof.

Each of the reasons Cavanaugh cites for not accepting CSST has a counter-argument from the manufacturers. The argument over whether or not to accept CSST in building codes is being fought presently and most publicly in the state of California.

In the meantime, IAPMO is trying to promote its set of building codes, the Uniform Plumbing Code (UPC) and the Uniform Mechanical Code (UMC) to be the standard body of plumbing and mechanical codes in the United States. For this to happen, IAPMO needs to be listed by ANSI. However, this requires some degree of cooperation with existing national code developers - including the National Fire Protection Association (NFPA), whose code covers fuel gas piping and accepts CSST. In the mid-1990s, IAPMO partnered with NFPA (which is ANSI listed) and incorporated all of the language used in NFPA.54.

This opened the door for CSST to be used where local codes would allow. In California, CSST was used extensively under the allowance of local codes. It became a favored material not only because of its time-saving capabilities, but because of its resistance to damage in earthquakes. Factory Mutual Research has approved CSST for flammable gas piping systems - meaning it has been tested in seismic simulations alongside black pipe. In Japan's, where earthquakes are an even greater threat than California, the largest cities require CSST for residential gas piping.

Even with all of its practical advantages, CSST is not the industry standard. Even though CSST is both ANSI listed and NFPA certified, IAPMO still has not recognized the material, which is the main obstacle keeping CSST from widespread use in areas such as New York City, Chicago and California. Note, that is widespread use. It is already being used in most jurisdictions via local variances in fuel gas codes.