**Draft**

Prepared by: Dan Robles, PE
Community Engineering Services, PLLC

 

Abstract: Engineering and construction management oversight can help assure that epoxy pipe liner applications are sold and performed with the expectation that professional standards must be applied, and independent testing must be performed, as a condition of the contract bidding price, bank funding, insurability, and associated warranty claims.

Introduction: This study was conducted upon request from a homeowners association as part of a wider investigation into appropriate technologies for renewing an aging galvanized potable water system. The concern is that a relative lack of balanced and factual information is available to the HOA regarding the risks and consequences of committing to epoxy pipe liner technology for repair and renewal of their potable water systems as an alternative to complete re-piping of their structure.

This case study is conducted from a small sample of epoxy failures encountered in the Pacific Northwest. The case study attempts to focus on vulnerabilities of all epoxy applications and does not attempt to isolate a particular supplier or contractor.

The greatest determinant of success or failure is the training and experience of the epoxy applicators specific to the characteristics of the system being renewed. Unfortunately, there are very few reliable methods to test an application and no option to mitigate application failures, except to re-pipe, anyway.Epoxy is a remarkable substance and it is assumed that Epoxy can be applied correctly, but the cost of doing so may match or exceed the cost of a re-pipe in modern materials. This report applies to Galvanized steel substrate.

Summary Conclusions:

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 Following recommendations are provided for the HOA association when evaluating and Epoxy liner solutions for potable water system renewal:

1. Perform a condition assessment to determine remaining material at pitting and threaded areas.  Epoxy does not provide any structural reinforcement of the pipe.

2. Review the quality manuals of the contractor for compliance with the governing documents for epoxy liner application.

3. Enforce, record, and document the testing and inspection at time of application and reconcile with ASTM standards.

4. Perform random destructive testing near completion of project when contraction is still on site to repair test section.  Consider re-testing near the end of the warrantee period.

5. Identify, in writing, the contingency plan should any test or inspection fail at time of commissioning, or should a failure occur over the life of the warrantee period.

6.  Assure that contractor warrantee matches epoxy manufacturers warrantee.

This paper is organized into four sections. 

1. An introduction to the epoxy liner process identifies the major process components, relevant industry claims, and relevant counter claims.

2. The literature review covers relevant search engine results for epoxy failures as well as governing documents for the epoxy application process. Epoxy liner failure modes are established.

3. This case study provides photographic demonstrations of actual epoxy liner failures on galvanized pipe in the Pacific North West area.

4. The final section compares the actual sample with the known failure modes, quality assurance vulnerabilities, and promotional literature specified in the prior sections.

SECTION 1: Introduction to 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 removes corrosion and oxidation in order to prepare the pipe walls to accept adhesion of the epoxy liner.  Once prepared, the epoxy is blown through the pipes in a liquid state using pressurized air where surface tension assures complete and uniform coating of the surface. The epoxy is the “cured in place” either by the application of heat and/or the passage of time (pot life).

Claimed benefits:  The following select claims are paraphrased from publicly available epoxy industry literature.

  • An epoxy lining delivers benefits that re-piping cannot.
  • More durable than copper pipe, with a lifespan of 40 – 60 years
  • Testing engineers estimate the life expectancy of the epoxy is roughly 100 years.
  • Safer for drinking water than unlined metal or cement pipes
  • Less mess, cost and time than pipe replacement
  • Eliminates corrosion that leads to blocked and leaky pipes
  • Pipe lining is as much as 50 percent less expensive than traditional pipe replacement costs.
  • Epoxy lining can be performed in any metal pipe in any building, structure, or environment, above or below ground
  • Lining prevents toxic heavy metals from leaching into drinking water and prevents leaks and breaks in pipe systems.

Counter Claims:  The following select claims are paraphrased from plumbing and mechanical contractor sources [5].

  •  Epoxy Applicators alter a plumbing system design without prior assessment
  • Difficult to test and inspect pipe de-scaling/cleaning process and epoxy adhesion.
  •  Epoxy is permanent, if epoxy adhesion fails inspection and/or test, then what? Must re-pipe anyway.
  •  Must maintain epoxy continuity, difficult to make changes, cuts, repairs, or add on. Must repipe anyway.
  •  Epoxy is a brittle substance vulnerable to mechanical stress such as cutting, vibration, thermal expansion, bending, etc.
  •  Proper adhesion is a deeply technical process requiring close quality controls by highly trained professionals.
  •  Reduction in pipe diameter may not comply with original codes.
  •  Compliance with current building, permitting, and performance codes unknown.
  •  Possible pooling and ridging of epoxy causing turbulence and turbidity.

SECTION 2: Literature Review

This section is not meant to be an exhaustive academic literature, rather, it represents most likely results available to an HOA researcher conducting a search engine evaluation of the product at the time of this writing.  Similar results would be available to a moderately technical homeowner considering the use of epoxy lining technology.

[1] Impact 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.  This document provides a broad and useful description of the epoxy chemistry.  The paper provides a literature review citing relevant industry standards for water quality while as well as laboratory tests and case studies produced by the authors. The results of the study confirmed most existing data that reports that properly-installed epoxy linings have a minimal impact on water quality parameters unless mixed improperly.

[2] Epoxy Adhesison Testing Sponsored by the Texas Department of Transportation and used to develop simple and reliable tests for epoxy adhesion to metal bars used in reinforced concrete.  While re-bar epoxies may use a different chemistry and curing method as potable water systems, it is instructive nonetheless as the goal is to adhere to and waterproof the metal surface.  The two tests include a “rust test” and a “knife blade test”.  In effect, they wet the sample and look for rust and they apply a shear force to the epoxy and observe adhesion.  Both conditions are present in potable water systems. As such this study is included in our lit review.

[3] PUBLIC 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.  This document specifies process and contractor qualifications, controls, tests, and submittals for use of Epoxy Liner in potable water systems applicable to Army and other military facilities. Emphasis is placed on quality control of the application process, submittals at progressive stages of the work, material and performance to industry and military standards, as well as testing and inspection specification.

[4] INVESTIGATION REPORT ON THE FAILURE OF MAKKAH-TAIF WATER TR  This paper documents one of the few published failure sequences that I was able to find in a public search.  The applicability is on large potable water pipes (24-36 inch diameter) rather than small domestic systems.  The benefit however is the ability to control the surface preparation and inspection of such a large pipe.  Notable outcomes are that the failure modes are very similar to those that we did in fact find in smaller domestic pipes.  This allows us to isolate the characteristics of the epoxy itself independent of the surface preparation.

[5] Canadian law suit brought against the epoxy applicators by a plumbing company. The claims of this suit allow us to form the basis of counterclaims to contracts with the epoxy industry advertisement.  These claims are derived from the opinion of professional trades whose bias is to replace piping systems when they get old.  Among the claims is that a comprehensive condition assessment of the piping system is performed.  The next citation in this lit review demonstrates what such a condition assessment may entail.

[6] Potable Water Pipe Condition Assessment For A High Rise Structure In The Pacific Northwest (Robles, Coles 2012).  The purpose of this condition assessment was to establish a minimum baseline condition for an existing potable water system.  Factors taken into consideration include water quality, serviceability  and structural integrity of the existing system.  Such measures are useful for the HOA in considering future remediation options as well as for future engineers and contractors for recommending technologies to improve the system.

[7] Layman’s Guide to Epoxy Paint / Coating Failures: This website authored by an expert in epoxy coatings contains a wealth of information about epoxy, applications, success stories and failures; balanced and comprehensive opinion. “Coatings fail for a number of reasons, the most common being moisture, dirt and contaminants, and natural breakdown and weathering. Careful selection of your coating, an understanding the possible causes of failure in your particular situation, and careful surface preparation will all significantly reduce the occurrence of coating failures.”

Governing Documents:

[8] NSF/ANSI Standard 61 Drinking Water System Components – Health Effects is the standard that establishes minimum health effects requirements for materials, components, products, or systems that contact drinking water, drinking water treatment chemicals, or both.

[9] AWWS C210-3; Liquid-Epoxy Coating Systems for the Interior and Exterior of Steel Water Pipelines; A published standard by the AWWA (American Water Works Association).  This document is cited in most epoxy liner publications including the above references herein.  The purpose of this standard is to provide the minimum requirements for liquid-epoxy coating systems for the interior and exterior of steel water pipelines, including material, application, inspection, testing, performance requirements, handling, and packaging requirements.

[10] ASTM F2831 – 12: Standard Practice for Internal Non Structural Epoxy Barrier Coating Material Used In Rehabilitation of Metallic Pressurized Piping Systems aggregates the multiple standards for testing, performance, labeling, preparation, inspection, etc. Included the following test specifications: D3359 Test Methods for Measuring Adhesion by Tape Test, D3363 Test Method for Film Hardness by Pencil Test, D4541 Test Method for Pull-Off Strength of Coatings Using Portable Adhesion Testers, etc. Purchased copy on file.

SECTION 3: Case Study; Introduction

Using Linkedin, Facebook, and several social media technologies, multiple sources were found who had witnessed epoxy liner field failures. 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 exception is a blocked pipe which failed immediately, but went undiscovered for a period of time after the contractor had left the job site  and the plumber was called to troubleshoot and inoperable fixture.

Sample:  The sample used in this case study represents six common components of a potable water system including:  3/4 Inch straight pipe, a Tee section with a 3/4 pipe fitted at one end and a reduction to a 1/2 inch brass fixture at the other end,  two 3/4 inch elbows in series with directional change, a large 2 inch elbow, a brass valve that has been rendered inoperable and coated as a coupling. Finally, an example is provided of a 3/4 inch pipe which experienced a complete blockage at the elbow and was not discovered by the epoxy process inspection.

The Straight Pipe section

The two straight pipe samples leading to both the Tee section and the blocked elbow appeared smooth and well applied. On closer review, the straight sections revealed a non-uniform thickness that exceeds recommended thickness of 4-10 mils [1], [2].

Application standards require close monitoring of the quantity of epoxy that enters a particular length of pipe as a means of determining completion of application.  If this standard was followed, then a corresponding deficit of epoxy thickness would appear elsewhere in the section.

 

The Tee Section

It is relatively easy to predict that the presence of a tee would create a difficult segment for both the cleansing medium as well as the epoxy coat.  In essence, each fluid must disorganize, split, change direction and reorganize – losing much of their momentum at single point.  Special considerations must be made for this type of transition.  The resulting poor preparation of the surface resulted in rapid epoxy failure.  Each Tee section represented different failures.  The  first transition goes to 3/4 galvanized pipe and the second connects to 1/2 inch line.  The brass fitting was applied after the epoxy and demonstrates no coating.  There is however a ring of water intrusion at the transition.  This would be typical of such a transition occurring is, say, a valve replacement or fixture update.

 

 

 

 

 

 

 

 

 

The Large Section; 2 – inch elbow

The large pipe offers us a view into the behavior of the sandblasting media and epoxy adhesion and texture upon curing.  Instead we find extensive rust nodulation covered somewhat by epoxy as well as a widespread failure of the epoxy adhesion.  There is a possibility that zinc may remain on the pipe – the galvanization cathode is know to be highly detrimental to proper epoxy adhesion. Any new replacement pipe must be stripped of it’s zinc plating prior to epoxy coating.

 

 

 

 

 

 

 

 

Inoperable Brass Valve

This gate valve was rendered inoperable for reasons likely associated with the lining process.  The valve service would likely have been moved elsewhere in the system.  In any case, the valve section offers a clear view of epoxy liner surface texture and adhesion properties upon brass fittings.

 

 

 

 

 

 

 

 

Serviceability:

Many failure modes in piping systems arise from the corrosion or breakage of brass valves.  Homeowners also need to periodically update their fixtures or add to their plumbing system.  Accidents such as collision with a pipe running through a parking garage or the introduction of filtration or other accessories all require an interface with the primary plumbing system.   Wherever the continuity of the epoxy liner is broken by cutting or unscrewing a connection, the introduction of water behind the coating becomes a hazard to the integrity of the coating.  the epoxy coater would need to be on hand to seal any repair at any time in the future. For this reason, serviceability is an important subject for the epoxy applicator to address.

Existing pipe conditions:

Galvanized steel often experiences the growth of nodules and scale on the inside surface of the pipe.  The material that builds these growths comes from the thickness of the pipe.  Large nodules are often accompanied by deep pitting. These pits can be quite numerous and deep often compromising the strength of the pipe – especially around threaded areas as the thread cuts deep into the original material and is pre-stressed by tightening. A comprehensive condition assessment of the pipe should be done prior to the application of the epoxy coating [6]

Observed wall thickness condition:   The following photographs represent areas that were discovered in a recent piping condition assessment for a client community considering an Epoxy Solution.  In some many places, less than 25% of wall original wall thickness material remains.

 

 

 

 

 

 

 

 

Pipe Threads: Pipe threads are cut on a tapered end and bind against each other accumulating stress as torque is applied to the adjoining pipes. These stresses remain in the steel as stored energy – like a spring can store energy when compressed and release energy when liberated.

 Observed threaded sections: Threaded sections are particularly vulnerable to failure because they are already under a highly stressed interference fit condition, a failure would likely propagate around the circumference of the pipe or provide a path for leakage or catastrophic high volume pipe failure.

 

 

 

 

 

 

 

 

 

Threaded section demonstrating active corrosion near thread root.  As little as 1 mm of material remains. The Epoxy Lining system removes additional material from the pipe wall.

Anatomy of an Epoxy Failure: (click to enlarge)

  

 

 

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.

As such, a poorly applied epoxy liner could weaken a pipe considerably. The result could be a catastrophic high-volume pipe failure requiring a high insurance payout, which would not otherwise be attributed to epoxy coating.

Section 4: Conclusion:

Epoxy coating of steel is a widespread practice in construction and mainline water service [2] [3] [4].  The failure modes and vulnerabilities of epoxy are widely known and highly consistant in their progression [7].  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 Engineers [3], The American Water Works Association [9], the American Society of Testing and Materials [10], the Society of Protective Coatings, etc., 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 would not occur.

A comprehensive collection of tests and inspection criteria have 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 adhesive when it is applied correctly [7].  The question arises that if an application should fail a test or inspection, what is the contingency plan to remediate the flaw?  How will the epoxy be removed and how will the re coating be applied?  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 warrantee claim would a failed test be covered and to what extent will coverage be warranted?

The serviceability issue is not trivial.  Homeowners must be comfortable with the idea that no further modifications, maintenance, or improvements can be made on their current potable water system.

Double Jeopardy: 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.  As such, a poorly applied epoxy liner could weaken a pipe considerably. 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 and independent testing will be done as a condition of the contract bidding and warranty claims so that they may adjust their pricing to meet customer expectations.   

 

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