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Pinhole Leaks in Copper Plumbing Systems

We are aware of a concern of some of our citizens regarding pinhole leaks in residential copper plumbing systems.  The Cobb County-Marietta Water Authority (CCMWA), is actively investigating this phenomenon, and has been for some time.  In 2012, CCMWA commissioned a study with HDR Engineering related to copper pitting and pinhole leaks in Cobb County.

The HDR Engineering Study (2012):

  • Evaluated copper piping samples removed from 4 homes that had experienced pinhole leaks.
  • Found no indications of poor copper quality.
  • Found no indications of a biological component to the copper corrosion.
  • Determined the common cause of copper corrosion was excessive solder flux, a result of poor soldering practices by the installing plumbing contractor.

As a follow-up to the 2012 study, CCMWA worked with experts at Virginia Polytechnic Institute and State University (Virginia Tech) to analyze sections of leaking copper pipe from residential plumbing in Cobb County and Paulding County to confirm what factors may be contributing to the problem.

The Virginia Polytechnic Institute and State University Study (2018):

  • Evaluated copper piping samples removed from 13 homes that had experienced pinhole leaks.
  • Found no indications of poor copper quality.
  • Pinholes may be more likely to occur in parts of the distribution system with relatively low levels of chlorine residuals or in homes with relatively low water use.
  • It was hypothesized that areas with low chlorine residuals may experience increased amounts of sulfate reducing bacteria (SRB) which may be an underlying cause of the pinholes found in these areas.  
  • In order to determine if there is a correlation, studies should be conducted to document chlorine residuals throughout the system to determine if increased levels of sulfate reducing bacteria (SRB) or pinhole leaks are present. 

CCMWA conducts chlorine sampling on nearly 500 individual taps in both Cobb County and Paulding County monthly and documents chlorine residuals throughout the system.  In March and April of 2018, CCMWA sampled taps in homes with documented pinhole leaks for sulfate reducing bacteria and found no SRB present.

Related facts about CCMWA water:

  • CMWA does not supply hard water; the average hardness is around 38 mg/L (as CaCO3).  On the USGS (United States Geological Survey) hardness scale, this is considered soft water.  The USGS hardness scale is as follows:
    • 0 to 60 mg/L -- soft
    • 61 to 120 mg/L -- moderately hard
    • 121 to 180 mg/L -- hard
    • 180 mg/L and greater -- very hard
  • CCMWA does not disinfect with chloramines; sodium hypochlorite is used for disinfection.
  • CCMWA's water is not acidic; corrosion control is accomplished by adding lime to increase the alkalinity and to keep the pH above 7, typically 7.9 (non-acidic).  This is one of the two corrosion control methods recognized by USEPA (U.S. Environmental Protection Agency).

CCMWA Works to Ensure Safe Drinking Water:

  • Drinking water provided by CCMWA is safe.  In 2022, both CCMWA water treatment plants received the Georgia Association of Water Professionals Platinum Award for meeting all water quality, monitoring, and reporting requirements for 13 consecutive years.
  • Lead and copper testing is conducted in homes in Cobb County, in accordance with USEPA's Lead and Copper Rule.
  • Testing in Cobb County has demonstrated full compliance with the Lead and Copper Rule.

Within this website, CCMWA has provided various technical articles and study results on copper pipe pitting and corrosion for your reference.  We hope you find the information provided to be helpful and insightful.  If you have further questions, please contact CCMWA's Water Quality Engineer, Patrick Pherson at 770-514-5213 or


Additional Resources:

Virginia Tech - Cobb County Pinhole Leak Report 3-13-2018

ATS Analysis of Cobb Residential Copper Pipes 9-2017

Cobb County-Marietta Water Authority Copper Corrosion Study 2013

Internal Corrosion Control in Water Distribution Systems, American Water Works Association

Pitting Corrosion of Copper in Waters with High Ph and Low Alkalinity , American Water Works Association

Optimal Corrosion Control Treatment Evaluation Technical Recommendations, United States Environmental Protection Agency

Drinking Water Requirements for States and Public Water Systems , United States Environmental Protection Agency

Pinhole Leaks in Copper Plumbing, Maryland Department of Housing & Community Development



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