Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.

If you've found help here, check back in to let us know how everything worked out.
It's a great way to thank those who helped you.
Need to contact us? Visit

copper pitting

Have a customer on city water where we replaced some water lines maybe 15 years ago. The copper water lines keep developing leaks--pitting. Leaking water lines have been replaced with PEX. We have not had other customers with this problem and have done a lot of work in this town. Any idea where his copper gremlins are coming from?


Henning's Plbg
LaOtto IN


  • canuckDalecanuckDale Member Posts: 77

    Well, you said 'Gremlins'??;-)

    Mostly the hot lines? Softener installed?

    Soft water above 140*F combined with undersized piping can cause aggressive pitting.

    ? Dale
  • eleft_4eleft_4 Member Posts: 509
    elect. grounding problem???


  • Jens SorensenJens Sorensen Member Posts: 9
    more info

    Leaks have been mostly in cold water, in the pipes, not the fittings. No circulator pump. Replaced main water feed, piping for softener.

    Thanks for you help so far.

  • kevinkevin Member Posts: 420
    water Hardness

    How hard is the water? what is the amount of salt consumed pper month? is it set too high? is the water discolored in any way? Check the toilet tanks for anything unusual..sediment, copper, blue coloration, etc.
  • Mark Eatherton1Mark Eatherton1 Member Posts: 2,542
    Sounds like...

    cold water pitting. In areas with relatively soft water, the new copper lines do not get a protective coating of lime scale, and the alum used as a coagulant in the water treatment process embeds ions of aluminum, which set up a dissimlar metal mix and eventual internal pitting and leakage. You'll probably never get the local water authority to admit to it, but that's where I suspect it's coming from.

    Here's something I found at Google.





    In response to increasing reports of copper pipe pinhole leaks in spring / summer of 2000, WSSC launched an aggressive investigation.
    Task force was formed – WSSC, copper and master plumbing associations, County representatives and copper corrosion experts, including: Dr. Marc Edwards of Virginia Tech, Dr. Steve Reiber of HDR Engineering and Richard Lewis of Richard Lewis Engineering.
    To date, more than 4,300 customers have reported copper pipe pinhole leaks and have completed questionnaires. Observations on data from questionnaires include:
    -- Majority of pinhole leaks being reported are in cold water horizontal copper piping.

    -- Majority of pinhole leaks being reported are in the older areas of Montgomery and Prince George’s Counties.

    -- Nearly 80 percent of the reports received thus far involved homes built prior to 1970.

    -- Copper plumbing has been used extensively in the WSSC service area for more than 50 years. Regardless of the age of the pipes, however, the majority of pinhole leaks reported to WSSC thus far through our questionnaire first occurred in the mid-1990s.

    -- Customers living in and around the older communities of Beltsville, Laurel, Bethesda, Chevy Chase and Silver Spring are reporting the most occurrences of pinhole leaks in copper pipes.

    While it’s likely we will never know the exact cause of the majority of pinhole leaks in our service area, we are working as an advocate for our customers and we believe we are in the best position to help minimize these occurrences for them.


    Experts have been focusing on water chemistry, previous copper corrosion research, comparing pinhole leak occurrences in the WSSC service area to other areas of the country, water treatment modifications that may minimize copper pipe pinhole leaks and metallurgical examinations of copper pipes.


    Drs. Edwards and Reiber reviewed records of WSSC’s finished water chemistry and water treatment practices. They could not find any obvious reason why WSSC customers should experience high levels of copper pipe pinholes.
    Metallurgical examinations of copper pipes with pits revealed deposits of aluminum hydroxide, silica, and iron hydroxide on the interior surfaces.
    In laboratory tests, there were greater levels of corrosion activity, (but not necessarily pinhole corrosion), when aluminum solids and chlorine were present together, than when either was present alone.
    Sources of aluminum include raw water, coagulant used in water treatment process and water mains.
    Potomac plant’s median residual aluminum level is 1/3 less than the median observed nationally, and the Patuxent Water Filtration Plant’s level is about 2/3 less than that observed nationally. Limited sampling indicated possible leaching of aluminum from the distribution system – both new pipes and recently cleaned / lined pipes.
    Aluminum deposits on copper pipes in WSSC customers’ homes are similar to those found in Denver, where pitting is not known to occur. Deposits by themselves do not appear to be the sole initiator of the leaks.
    In lab tests, orthophosphate and polyphosphate were effective at stopping pitting. Neither caused temporary increase in general corrosion at high dosages.
    Phosphates are completely safe, federally approved water additives used by more than 50% of utilities nationwide (Rockville, Carroll and Fairfax counties) to combat corrosion-related problems.


    One interesting theory being advanced by Dr. Edwards involves the removal of natural organic matter (NOM) by water utilities across the Country. NOM includes many different organic chemicals in rivers and reservoirs from sources such as decaying leaves. As part of ongoing efforts to improve water quality and enhance public health, the Environmental Protection Agency (EPA) required water utilities nationwide to optimize treatment processes in the mid-1990s to remove more NOM. It had been widely understood by corrosion experts that some of the chemicals making up the NOM act as corrosion inhibitors and protect metal piping. With the EPA ruling requiring utilities -- including WSSC -- to remove more NOM, Dr. Edwards theorizes that this has increased copper corrosion and pinhole leak activity across the country.

    Dr. Edwards also theorizes that the standard industry practice of cleaning and lining older water mains with cement mortar, along with other unknown factors, may play a role in this phenomenon. Dr. Edwards emphasizes, however, that both of his theories are unproven. Because this issue is impacting homeowners across Maryland and the Country, he is pursuing funding for additional research into this issue at the national level.



    Our short-term plan includes using orthophosphate in a pinhole leak prevention pilot in a local apartment building that has experienced a high frequency of pinhole leaks. The pilot program began in late April 2002 and should last approximately six months. In our laboratory tests, orthophosphate was effective in stopping pinhole leak activity. With approximately 50 percent of utilities nationwide using phosphates, including Rockville, MD and Fairfax, VA, we are confident that adding orthophosphate to the treatment process is completely safe. Many water utilities have been safely using phosphates since the passage of the U.S. EPA’s Lead and Copper Rule (1992) to reduce lead and copper levels in tap water. Phosphates are FDA approved and used in many of our favorite foods / drinks, including: cheese; cakes; cookies; breads; crackers; powdered foods; cured meat; breakfast cereals; dehydrated potatoes; butter; chocolates; and soft drinks. Results of this pilot will help us determine potential system-wide application.


    Again, since similar kinds of copper pinhole leaks have occurred, and are occurring, elsewhere in Maryland, the Country and the world, we are hopeful our investigation will launch a broader study on this issue. Therefore, our long-term plan includes trying to determine what other factor(s) potentially play a role in causing these leaks. We also want to investigate the most likely sources(s) of the deposits found on the interior surface of the pipes and other potential actions to address this problem. Additionally, we recommend continuing research on the copper pipe manufacturing process and its possible role in predisposing some pipes to pitting. We also will assist Dr. Edwards in his pursuit of funding for additional research at the national level.

    To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"
  • hrhr Member Posts: 6,106
    Copper pitting

    I would start with some manuals from the Copper Development Association. There are many reasons that these problems develop. Water conditions play a big part generally, and as others mention electrolsis, erosion corrosion, and more.
    The CDA also has regional offices with phone support. Happy hunting!

    hot rod

    To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"
This discussion has been closed.


It looks like you're new here. If you want to get involved, click one of these buttons!