In-Place Rehabilitation of Small-Diameter Piping Systems
In situ or in-place rehabilitation of existing water mains and water-related structures had its infancy in the United Kingdom in the 1970s and has since developed into a reliable, cost-effective and long-term rehabilitation method for potable water pipes, water storage and distribution systems, with application now accepted worldwide.
In the United States over the past two decades, methods have been commercially developed and patented that use epoxy-barrier-coating techniques which allow for the in-place rehabilitation of small-diameter piping systems. (For purposes of this article, small diameter means those comprised of pipes 2” and less.) The result has been the use of in-place rehabilitation of small-diameter piping systems in commercial buildings, schools, hotels, hospitals and single-family homes.
This article will address both historical and current developments of the in-place rehabilitation process. In-place rehabilitation (also called pipe restoration) was developed to be an alternative to conventional re-piping techniques. It is applied in a cost-efficient manner to combat corrosion and other factors that reduce the life of a piping system, as well as to reduce the leaching of harmful metals (such as lead or excessive copper) into the drinking water supply.
Regulatory Process and ApprovalsThe process of approving the epoxy lining material and its application falls under three primary categories: health, physical properties and code compliance. The lining material referred to as a “coating” has to be approved and safe for contact with drinking water, meet industry standards for adhesion and durability, and be applied to meet existing plumbing codes. Standards have been adopted by both IAPMO and ICC-ES relating to the process and coatings applied.
IAPMO has adopted the IAPMO Guide Criteria for Internal Pipe Epoxy Barrier Coating Material for Application In Pressurized (Closed) Water Piping Systems. Originally adopted as IGC 189-2003, several updates have brought the Interim Guide Criteria to its current version, IGC 189-2008, which covers applications of epoxy lining to both metallic and non-metallic piping systems. This standard covers minimum standards for the manufacture and performance of epoxy barrier coatings mechanically applied to the interior surfaces of piping systems. It is intended to prescribe minimum test performance and test requirements for such coatings and application, and includes referenced standards:
ICC-ES approved Internal Epoxy Coating Pipe Material Acceptance Criteria (AC 298) in Oct. 2005. This criteria was intended to establish the minimum criteria necessary for the use of a proprietary, mechanically mixed, blended, epoxy barrier coating that is mechanically applied to the interior of pressurized water pipes. Codes and Reference Standards include: 2003 International Plumbing Code and 2003 International Residential Code of the International Code Council; NSF 61-2004, Drinking Water System Components - Health Effects, National Sanitation Foundation; and the above listed ASTM and AWWA standards.
AC 298 expanded on IAPMO’s IGC 189 and addressed pipe-cleaning standards, the effects of the lining material on flow rates pressure loss and further established evaluation report verification criteria. In 2007, ICC-ES auditors completed the first Evaluation Service Report (based on AC 298) on the ACE DuraFlo ePIPE patented method of pipe restoration (ESR#1390).
Basics of Pipe RestorationVarious approaches to pipe restoration are used in the business. However, most encompass six basic steps: evaluating the piping system and isolating it, draining water from the pipes and air drying the pipes, cleaning and profiling the pipes’ interior, epoxy coating the pipes, reassembly and testing the system. A more detailed step-by-step description follows. Also see Figure 1.
Step One - Problem Diagnosis
Step Two - Project Planning and Setup
Step Three – Draining and Air Drying Pipes
Step Five - Corrosion Control Epoxy Coating
Step Six - System Evaluation and Re-Assembly
Figures 2a, 2b and 2c show the before-and-after effects of this epoxy-lining treatment on pipe. Figure 2a shows the inside of a copper pipe that has pinholes, while Figure 2b shows a rehabilitated copper pipe with an epoxy lining. Figure 2c shows a heavily-corroded pipe made of galvanized steel.
Epoxy Lining PerformanceLong-term durability of an applied epoxy lining depends on various factors related to resin formulation and contractor performance, including:
In view of these factors and their various potential combinations, it is apparent that the behavior of lining systems could differ greatly even within an individual rehabilitation, making it difficult to assess an open-ended statement of long-term durability.
However, long-term durability of epoxy lining can be approached from a number of fronts, including: examination of known testing data, examination of coated samples of previous applications and the documented history of epoxy coating performance.
Corrosion control by the use of protective barrier coatings has progressed to a scientific level. This allows engineers and utilities to make reliable predictions and selections regarding specific corrosive conditions and coatings, and to use a selected coating to prevent corrosion and reduce the leaching of harmful metals into the water supply from metallic piping systems.
Results of various performance laboratory tests on different coating systems play a major role in this exercise. Such performance results form the basis in establishing their correlation with field performance and predicting the long-term life expectancy of the barrier coating. The adhesion of a barrier coating is generally considered to be a good indicator of its longevity. The greater a coating’s adhesion to the substrate, the longer it will last.1
The adhesion standards established by the American Water Works for epoxy-lined pipes is 400 psi.2 The adhesion of the small-piping potable water product exceeded 3,500 psi.3 This pipe’s flow rate, velocity and friction loss is shown in Figure 3.
Examination of Coated Samples of Previous Applications
The history of epoxy barrier coatings is a history of adaptation and change in formulation as performance criteria has become better known - especially since epoxy lining of substrate for corrosion control became popular in the 1970s. Leading the way in studies related to longevity, based on exhumed samples, has been research conducted on behalf of the WRc (Water Research Centre) of the UK.
In conclusion of their studies, the WRc wrote the following in Operational Guidelines and Code of Practice Manual about in situ epoxy resin lining: “In addition, the good durability (in excess of 75 years)4 and minimal reduction in hydraulic carrying capacity5 of the epoxy resin process provide an excellent alternative to cement mortar for small-diameter pipes and, in particular, those carrying soft water.” 6
Further conclusions based on studies of some 82 exhumed pipe samples - ranging in age from 4 days to 14 years - lead to the following comments: “The overall impression from the study is that epoxy linings are very durable and that, with current formulations, application equipment and quality assurance procedures, a 30- to 50-year life can be readily achieved.” 7
In Vancouver, Canada, a paper published in 1999, entitled Epoxy Coating of Pipe Systems, focused partially on epoxy coating vs. conventional pipe replacement. General comments and summary findings in the report stated in part: “Assuming that the epoxy was adequately applied and that it will then perform in a similar fashion to epoxy coatings applied by conventional methods, it is reasonable to expect the epoxy coating to remain intact for the life of the building (over 100 years).” 8
The American Water Works Association engineering department, in their assessment of rehabilitation technologies available for reducing or eliminating pipe failures, rates lining existing pipes to combat internal corrosion highest on the list of operational strategies that could be adopted by water utilities. They also provide a longevity rating of 30 to 50 years of extended life for a pipe that is internally coated using epoxy linings.9
My company has applied epoxy coatings in numerous settings dating back to the early 1990s. Epoxy coatings were applied in a variety of conditions and on a variety of substrates (i.e., steel, concrete, copper, PVC, PEX). Applications covered a wide spectrum of corrosion-control projects, including water storage tanks, pipe lines, manholes, storm drains, hatchery tanks and wastewater treatment systems.
Protective coating projects have been completed for numerous civil agencies, including the East Bay Municipal Utility District (EBMUD) in the San Francisco area. EBMUD supplies water and provides wastewater treatment for parts of Alameda and Contra Costa counties on the eastern side of San Francisco Bay in northern California.
Approximately 1.3 million people are served by EBMUD’s water system encompassing the major cities of Oakland and Berkeley. The wastewater system serves approximately 640,000 people in an 83-square-mile area along the Bay’s east shore.
Additionally, the predecessor formula was used to rehabilitate an entire existing water treatment plant for the City of San Diego. Due to this project’s exceptional pre-construction engineering, during-construction documentation, and follow-up inspections, it was used as an Awwa-RF (American Water Works Association Research Foundation) research project to study the corrosion effects of enhanced coagulation on water treatment plant infrastructure.10
In Southern California, as part of a study of protective coatings, the County Sanitation District of Los Angeles County developed a test of protective coatings placed in a highly corrosive environment. This environment included a simulated wastewater facility with the coating material and substrate being exposed to a 10% sulfuric acid solution. After one year of evaluation, the predecessor-based formula was one of the few protective coatings to survive in this highly corrosive environment.11
Documented History of Epoxy Coating Performance
In more recent history and in the direct application into small-diameter potable water lines, sections of pipes from projects completed by my company have been examined. Long-term monitoring of its epoxy lining that was placed in the potable water system of two Seattle hotels in early 2000 shows the lining material performing to specification. This is consistent with the long-term history of epoxy coatings found in studies completed by the Water Research Centre and published findings of the American Water Works Association.
Who Chooses Restoration over Re-piping?Today, numerous consumer groups, engineers and installer groups have added in-place pipe restoration as one of their product choices. Installer groups include many of the major branded plumbing companies (Mr. Rooter, Roto-Rooter, Ben Franklin) and leak-detection providers such as American Leak Detection.
Engineers who recognize the benefits of combating corrosion and life extension of an existing piping system - especially when dealing with historical properties where access is limited - have chosen pipe restoration. Recently, engineers at the historic Willard Intercontinental Hotel (Figure 4) located in Washington, DC, chose to epoxy line the domestic hot water piping system over a conventional re-piping (see sidebar below).
However, application of pipe restoration is not limited to buildings. British Petroleum engineers recently chose to protect the potable water piping system aboard the world’s largest oil platform, Atlantis, located off shore in the Gulf of Mexico.
When is Pipe Restoration Right for a Project?Typically, the first step to answering this question is assessing the problem within the existing piping system. Problems could relate to excessive lead or copper leaching, low water flow, discolored water, or pinhole leaks. Placement of a barrier coating has also opened up the ability to provide a preventive or life-extension strategy to existing piping systems.
Secondly, you need to consider the location of the pipes, ease of access for traditional repair or replacement, and overall condition of the pipes or the complexity of access. Finally, you’ll need to compare the cost of restoration versus pipe replacement.
When making the comparison, you need to compare “apples to apples.” To do this, remember that pipe restoration requires little destruction and put back to a building’s features, and is often completed faster with less disruption to a facility’s use than conventional repair methods.
Case Study: Repiping the Willard IntercontinentalKnown as “the Crown Jewel of Pennsylvania Avenue,” the Willard Intercontinental Hotel is a historical icon in the social and political life of Washington, DC. However, the hotel needed to resolve recurrent pinhole leaks and replace inoperable isolation valves in their copper hot water piping. Pipe replacement was not an acceptable option because of the requisite guest intrusion, project duration, marble tub surrounds, unmatchable wall coverings, unavoidable dust, noise from demolition/reconstruction and the inevitable loss of business that is always an aspect of repipe.
Fortunately, Willard staff had learned of the ePIPE technology and requested a proposal with a host of special requirements: variable rate of restoration according to hotel availability, all rooms available for occupancy on busy mid-week nights, reconciliation of work schedule with the Secret Service’s high-security schedule, and the ability to adjust the schedule should any unscheduled changes be necessary.
Secret Service required the entire project to be shut down during visits by high-profile guests. To achieve this, valve installations were done in the overnight hours by strategically placing equipment, utilizing radio ear-buds and suspending hoses on the exterior of the building.
References1 Guan S, PhD and Kennedy H, B.Sc., MBA. A Performance Evaluation of Internal Linings For Municipal Pipe. 1996 North American Corrosion Engineers, Denver, CO.
2 AWWA, American Water Works Association. C210-97 Liquid Epoxy Coating Systems For the Interior and Exterior of Steel Water Pipelines, Feb. 1998, Denver, CO.
3 Mills G and Associates. Laboratory Testing Data ACE DuraFlo ePIPE, Humble, TX, Dec. 2001.
4 Warren IC and Crathorne B. The Development of an Epoxy Resin Relining System for Potable Water Mains. Proc IWSA Conference “Rehabilitation of Mains and Pipelines”, Berlin 1989. Water Supply, pp151-155, 1990.
5 Ewan VJ. A Study of the Effects of Relining On Leakage and Hydraulic Performance of Small Diameter Mains. External Report ER 185E, Water Research Centre (WRc), Swindon UK, 1986.
6 Warren IC. In Situ Epoxy Resin Lining – Operational Guidelines and Code of Practice. Water Research Centre (WRc), Swindon, UK 1989.
7 Protective Coatings Europe. Using Epoxy Linings to Rehabilitate Potable Water Systems, Pittsburgh, PA, March 1998.
8 McCuaig J, P. Eng. Epoxy Coating of Pipe Systems, Vancouver, Canada 1999.
9 AWWA, American Water Works Service Co. Inc., Engineering Department. Deteriorating Buried Infrastructure Management Challenges and Strategies, White Paper directed by USEPA, May 2002.
10 Edwards M. Dr., Williams S.A., Fernandez E. Case study. Epoxy Lining, Otay treatment plant, City of San Diego, 2002.
11 Render JA., Hsi R., Esfandi E., Sydney R., Evaluation of Protective Coatings for Concrete. County Sanitation Districts of Los Angeles, Whittier California, August 1998.