Epoxy is a magnificent substance used in many important applications where strength, hardness, moisture protection and strong adhesion are a requirement. Epoxy coatings are used to protect industrial applications from factory floors to reinforcement bar embedded in concrete. When applied correctly to a strong surface, few coatings are as tough as epoxy.
Recently, epoxy manufacturers have developed a lining process to coat the inside of an old potable water system with epoxy. This method is touted as a fast, 60 year, non-invasive, and inexpensive alternative to re-piping a whole building. However, when applied incorrectly, epoxy coatings can create a dangerous sense of false security especially where hidden from view such as the internal surface of a pipe.
Many epoxy failures are appearing in the field where litigation is often protected by gag orders thereby never reaching the public domain. This document identifies a wrinkle in the market that supports the rapid liner industry as well as the consequences of an unseen failure, should they occur.
This article arrives at the following conclusions:
- The potential for epoxy liner failures may be high in galvanized steel potable water systems.
- There is no reliable way to inspect the adhesion of epoxy inside a pipe.
- If an adhesion failure is found, there is no practical way to repair it except re-pipe — so, why not just re-pipe?
- Epoxy liner failures may typically occur at the precise location where the galvanized steel pipe is already at its weakest.
These observations are very important for the insurance underwriter who would otherwise classify a water system that has been repaired with epoxy liner as a "new" system. These observations are important for the forensic analyst that may determine the cause of a major water system failure on a condition other than being weakened by the epoxy coating. These observations are very important to the insurance broker who may inadvertently force a condominium community into an epoxy liner "solution" as a condition for maintaining coverage on their property.
Insurers should allow their condominium clients to perform a condition assessment without threat of cancellation. A small leak does not necessarily mean that the big rupture is imminent. In any case, epoxy does very little to eliminate the risk of a large rupture and possibly increases the likelihood. Then the insurance industry should work with the community to save enough money to perform a superior re-pipe with new materials such as polypropylene or copper. Together, a strong case can be made for the reserves or lending process. In the long run, a superior re-pipe may cost several times less than an epoxy "solution."
The Vicious Circle
Something as simple as a pinhole leak can generate thousands of dollars of water damage claims. Imagine what a fracture in a main riser cascading down 10 floors of luxury condos can cost? Unfortunately, many insurance underwriters believe that after a few small water claims, the big one is imminent. This may not necessarily be the case. Yet, many a condo is put on notice that they will lose their coverage unless the whole system is immediately replaced.
Long before the first pinhole leak, insurance companies stipulate in their policies that they are not responsible for a pipe failure if the condominium board is aware of the problem and fails to take corrective action. This condition essentially removes the incentive for the condo board to perform a quantitative piping condition assessment — if they don't know that there is a problem, they are insured. If they do know that there is a problem, they are not insured. This creates a compound moral hazard because they have no basis for saving reserve funds for a replacement.
After awhile, a few small leaks may appear leading to some minor insurance claims — this can trigger the threat of insurance cancellation for the condo. But this is the least of their worries; the condominium construction market is renowned for litigation, and many insurance companies make it very difficult or impossible for a contractor to be insured for condominium work. Condominium homeowners associations quickly learn that many contractors are simply unable or unwilling to work on condominiums.
If the homeowners association fails to save for a re-piping project, they are forced into an expensive bank loan from lenders who are equally wary of litigation ... this can become a huge mess far beyond the knowledge and capability of a condo board to manage effectively. The inability to manage a project in a litigious environment leads invariably to more litigation!
Herein lies the wrinkle in the market caused largely by the insurance industry betting against itself thereby creating a vicious circle that has very little to do with actual plumbing. In the midst of this condo / contractor / insurance / banking madness arises the epoxy liner salesman who is quick to provide everyone with exactly what they need — a cheap, fast fix.
The Epoxy Liner Process
The epoxy liner process involves isolation of sections of the existing pipe, drying the pipes with hot air and then sandblasting the inside walls with pressurized air and an abrasive mineral that is supposed to remove all corrosion, leaving bare metal in order to prepare the pipe walls to accept adhesion of the epoxy liner. Once prepared, the paint-like epoxy is blown through the pipes in a liquid state using pressurized air. The epoxy is then "cured in place" either by the application of heat and/or the passage of time (pot life).
A Case Study
A reputable plumbing contractor in the Seattle Area provided samples of epoxy liner sections that were removed from at least three properties and which failed within 4-7 years of entering service.
The following video demonstrates common epoxy liner failure modes correlated to available literature on epoxy liner vulnerability. The most common vulnerabilities of the epoxy lining system are associated with the planning and quality of the preparation as well as training of the applicator personnel.
The Anatomy of an Epoxy Failure: The following photographs demonstrate the progression of an epoxy failure where the surface has been improperly prepared.
When an epoxy failure does happen, it is likely to occur at the location where the pipe is already at it's weakest — pitted areas and threads.
Pipe threads are especially vulnerable: The photo below shows corrosion in steel pipe near pipe threads. Sandblasting with epoxy would weaken the threaded area further. A crack in the epoxy at this location would allow the corrosion to continue unknown to the residents. In many cases the existing pipe is better off left alone until a full re-pipe can take place.
Epoxy coating of steel is a widespread practice in construction and mainline water service2 3 4. While epoxy is tested safe to drinking quality standards by independent studies1 and national water quality standards6, any such "certification" is dependent upon actual adhesion to the surface of the pipe. The failure modes and vulnerabilities of epoxy are widely known and highly consistent in the progression7 of adhesion failure. It is also widely recognized that the project planning, surface preparation, and precise measurement and application of the ingredients to the substrate are the most significant variables in determining the probability of a successful epoxy coating assignment.
These factors are addressed in significant detail by the U.S. Army Corp of Engineers3, The American Water Works Association9, the American Society of Testing and Materials10, the Society of Protective Coatings, etc., who have all developed standards for the planning, preparation, measurement, and application of epoxy coatings. It can be assumed that if, and only if, these standards are followed and documented, then failures in epoxy coatings will not occur.
A comprehensive collection of tests and inspection criteria has been developed for epoxy coatings in any number of applications including internal water pipe coatings.3 Such tests as the knife blade test or those tests specified in ASTM F2831 are simple, fast and conclusive.10
The Epoxy Paradox
Epoxy coating is extremely strong and adherent if, and only if, applied correctly.7 The question arises that if an application should fail a test, inspection, or in service, what is the contingency plan to remediate the flaw? How will the epoxy be removed and how will the re-coating be applied? If re-pipe is the answer, why wasn't re-pipe considered in lieu of epoxy in the first place? If a single failure is found, what test sampling strategy must be applied to give a high likelihood that no other flaws exist in the system? Under what warranty claim would a failure be covered and to what extent will total coverage be warranted? These questions would be imminent in any litigation related to epoxy failures.5
Double Jeopardy: When an epoxy failure does happen, it is likely to occur at the location where the pipe is already at its weakest; i.e., pitted areas and threads. As such, a poorly applied epoxy liner could weaken a pipe considerably.6 The result could be a catastrophic high-volume pipe failure requiring a high insurance payout, which would not otherwise be attributed to epoxy coating.
Therefore, engineering and construction management representation and oversight can help assure that the epoxy liner material and contractors are aware of the expectation that industry standards will be applied. Independent testing should be applied as a condition of the contract bidding and warranty claims so that they may adjust their pricing to meet customer expectations. Again, epoxy is an amazing substance when applied correctly. But what if it is not?
1Impact of an Epoxy Pipe Lining Material on Distribution System Water Quality by Ryan Price and supervised by Andrea M. Dietrich, PhD., Chair, Environmental Engineering, Virginia Polytechnic Institute.
2Epoxy Adhesison Testing Sponsored by the Texas Department of Transportation.
3PUBLIC WORKS TECHNICAL BULLETIN 420-49-35 15 June 2001 IN-SITU EPOXY COATING FOR METALLIC PIPE; Department of The Army; U.S. Army Corp or Engineers.
10 ASTM F2831 - 12: Standard Practice for Internal Non Structural Epoxy Barrier Coating Material Used In Rehabilitation of Metallic Pressurized Piping Systems.
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