T.R. Consulting, Inc.

November 2002 Safety/Environmental Article


Flexible Piping Failures

By: Thomas Schruben – environmentalguy@aol.com

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Once again, tank owners are having trouble underground.  And once again, pipes are the source of the trouble.  As I write this article, I am reviewing reports of approximately 200 failures in double-walled flexible pipe systems in 11 states.  Many of the failures have occurred within four years of installation, and they seem to be increasing in frequency.  Some of the failures have been catastrophic, resulting in the release of thousands of gallons of product.  Some pipes have only swelled and have not released product.  For these reasons, some tank owners, regulators, and state-fund administrators are concerned that flexible-piping systems are not as reliable and long lived as they’d expected.  In a flashback to the mid 1980s, the facts are murky and data is scarce, preventing regulators and UST owners from making fully informed decisions.  Even the definition of “failure” is the source of many discussions.  One person’s cosmetic defect is another’s system failure. However, two conclusions are clear:  tank owners need to increase their vigilance for potential failures of flexible piping, and they should be ready to take swift action when failed piping is discovered.


A Brilliant Solution to an Intractable Problem


I’ve had a long history with UST system flexible piping.  From its conception, I was excited by the potential for flexible pipe to provide affordable, reliable secondary containment for petroleum products. In the late 1980s, while with U.S. EPA OUST, I participated in some of the initial discussions on the flexible-piping concept.  I then encouraged manufacturers to bring the concept to market.


In developing the 1988 UST regulations, we discovered that piping was a major source of leaks and that piping failures caused some of the largest releases.  As was discussed in the preamble to the final 1988 technical requirements for UST’s (40 CFR Part 280), EPA believed that while new tanks that were protected from corrosion showed a remarkable reduction in failure rate over unprotected steel tanks, and that adding spill buckets and overfill prevention devices could dramatically reduce the incidence of overfill releases, the failure rate of fiberglass piping did not differ as dramatically from that of unprotected steel piping.


We at EPA were so concerned about the possibility of future catastrophic piping failures that we required two forms of release detection for single-walled, pressurized piping in the 1988 technical standards.  Analysis of piping failures showed that many of the failures were related to the joints assembled in the field.  In addition, installers told EPA OUST that while double-walled fiberglass piping was available, it was very difficult to install, prone to failure, and too expensive for most UST owners.  Double-walled fiberglass piping systems had twice as many joints as single-walled systems, thus EPA was concerned that they would have twice the opportunity for problems. 


Flexible piping rolled out like a garden hose. It would eliminate most of the field-fabricated joints and promised easier installation than double-walled fiberglass piping.   The few joints that remained would be safely confined to secondary-containment sumps at the tank and under the dispensers.  At the time, it seemed to be a brilliant solution to an intractable problem.  The product was well received from its first introduction.   In 1997, EPA OUST listed seven manufacturers of flexible pipe (Survey of Flexible Piping Systems, March 1997, ICF Incorporated). 


Currently, five brands of flexible pipe are available in the US.  The 1998 upgrade deadline was a boon for flexible pipe, particularly in states that require secondary containment for piping.  The marketers of flexible piping were hard pressed to keep up with orders from owners who were looking for the reliability and security of secondary containment.


Early Troubleshooting


There were some early problems with flex pipe, but the regulators and many tank owners remained confident that the product would prove reliable.  While some of the problems were typical manufacturing problems that surface when any new product goes into mass production, some were unique. Over the years, several of the manufacturers have changed the design of their piping in response to product problems, while others have not experienced failures and thus have not changed their design. The March 1997 report from EPA OUST concludes that:


To date, problems with flexible-piping systems have been limited to fungal decay of first generation polyurethane-coated piping.  The fungal decay is mostly cosmetic and does not cause product failure, however, one manufacturer (Total Containment) has changed its outer layer construction to polyethylene and is in the process of replacing the polyurethane piping.  Most manufacturers are now marketing third and fourth generation products.  Problems with these systems have been infrequent, and manufacturers have stood by their products.  From an environmental protection standpoint, the performance of this technology to date has been excellent.


Recent Failures


The failure reports that I have received from regulators and the failures that I have investigated for my clients indicate that there are two distinct failure modes, which sometimes operate in tandem:




These failures are not confined to a single version of flexible pipe or to a single manufacturer. However, the early reports that I have reviewed show more failures with some brands than others and I have no reported failures for some of the brands.  The amount of pipe in the ground in total and for each brand is not known so I can not at this point determine if a particular brand of pipe is failing more frequently than another brand.  Also, it is not clear whether the failures are the result of installation error, shipping damage, defective manufacture, defective design, fuel incompatibility, other causes, or some combination of causes. 


The 11 states with failures that I have reviewed are principally in the South.  Several of the regulators and state fund administrators in northern states with whom I have spoken have not been aware of flexible-pipe failures in their states.  However, because owners may not be informing regulators of the piping failures that do not result in reportable releases, this apparent North-South geographic distribution may be related more to reporting than actual failure rates.


Because of these open questions, the regulators and state fund administrators that I have talked to are not ready to determine which, if any flexible piping is too unreliable, as the failures may be isolated to a few specific causes that do not affect all flexible piping installations equally. Clearly, more investigation will be needed before we get a full understanding of the failures and their causes.


Risk Management Actions


One aspect of the failures that is clear to regulators and owners alike is that the piping failures are too often compounded by leaks in sumps and failure of the release detection systems. Not only do sump leaks allow the petroleum to discharge to the environment, they can defeat the release detectors because the product does not fill the sump to the trip level of the liquid sensor.  In addition, malfunctioning release detection systems have allowed product to overflow the sumps and flow down the street before the failure was discovered. 


UST owners, state regulators, and state fund administrators are approaching this problem in different ways around the country.  The following risk management actions may be applicable in many situations:






The bright spot in this flexible pipe situation is that many of the failures have been discovered and caught by vigilant UST owners and regulators before they resulted in releases to the environment.  With further analysis of these failures and improved communication we can gain a clearer understanding of the root causes of these failures and find better ways to manage the risks. 


Thomas Schruben is an independent environmental risk management consultant.  He assists UST owners and state funds with environmental insurance, claims, and strategic planning.  He can be reached at environmentalguy@aol.com.