Ordering Information:
ORDER NUMBER:  91217
DATE AVAILABLE: Summer 2008

Printed Report		PDF
Subscribers	Order Report
Non-Subscriber	AWWA Bookstore (Sept. 2008)	N/A

[Note: to receive the supplemental CD-ROM which accompanies this report, please order the Printed version. The PDF file does not contain the supplemental material]

PRINCIPAL INVESTIGATORS:
Marc Edwards, Paolo Scardina, G.V. Loganathan, Darrell Bosch, and Sharon Dwyer

OBJECTIVES:
The purpose of this project was to assess the extent and implications of copper pitting and pinhole leaks for residential potable water plumbing systems. Additionally, the project team planned to investigate known and suspected causes of copper pitting and pinhole leaks through case studies at participating communities.

BACKGROUND:
Copper pitting that manifests into a pinhole leak greatly shortens the usable lifespan of potable plumbing pipes. The resulting leak can damage housing infrastructure and other valuables or potentially lead to mold growth. Homeowners, in turn, are adversely impacted by pinhole leaks and bear the financial burden associated with premature pipe failure. Unfortunately, factors that cause pinhole leaks and corresponding mitigation strategies are not well understood.

HIGHLIGHTS:
Pinhole leaks have been confirmed nationwide, and about 8.1 percent of homeowners (nationally) have experienced leaks. The total cost of pinhole leaks, including prevention, is $967 million. A number of different mechanisms were identified as the cause of pinhole leaks at participating communities including aggressive water quality, microbiologically-induced pitting, and hydrological factors.

APPROACH:
Multiple data sources were used to assess the extent of pinhole leaks. National surveys were conducted targeting plumbers, homeowners, businesses, and corrosion experts. The team also reviewed a database of copper failures spanning 30 years. The mechanistic causes of pinhole leaks were investigated via intensive case studies at participating communities, where hydrological, biological, and aqueous chemical factors were considered.

RESULTS/FINDINGS:
Pinhole leaks have been confirmed in all states and most major urban areas. Approximately 8.1 percent of homeowners nationally have experienced at least one pinhole leak and between 21–60 percent of homes in certain communities have observed pinhole leaks. The total cost of pinhole leaks and pinhole leak prevention in the United States is estimated at $967 million annually, with the largest proportion of cost ($564 million) in single family homes particularly devoted to repairs (44 percent). About 58 percent of responding water utilities reported using corrosion inhibitors, and annual costs of dosing corrosion inhibitors per customer (connection) ranged from $0.10 to $5.72 with an average of $1.16.

Case studies at communities experiencing pinhole leaks were designed to confirm suspected pinhole leaks and identify new mechanisms causing pinhole leaks. In terms of internal copper corrosion problems caused by unfavorable water chemistry and microbiology, three factors emerged with strong links to pinhole leaks: (1) high pH and high levels of disinfectant, exacerbated by aluminum and other particles, (2) local production of H2S in and around pits by sulfate reducing bacteria (SRB), and (3) erosion corrosion in hot water recirculation systems. Other factors are believed to influence pitting corrosion and pinhole leaks.

IMPACT:
The results of the various surveys demonstrate that copper pitting is a nationwide concern, particularly where certain unfavorable water chemistry and microbiological factors are present in the distribution system. The team developed a protocol to help utilities assess the extent of pinhole leaks in their community.

MULTIMEDIA:
The printed report is accompanied by a searchable CD-ROM that contains detailed case studies from the participating communities. The case studies include detailed information on the hydrological, biological, and aqueous chemical factors that led to copper pitting failures.

RESEARCH PARTNER:
USEPA

PARTICIPANTS:
Utilities from Florida, New Mexico, Tennessee, Ohio, Connecticut, and Iowa participated in this project.

ISBN 978-1-60573-017-2