Anyone ever seen pinhole leaks in the HOT pipes?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by AcidWater, Nov 21, 2008.

  1. AcidWater

    AcidWater Member

    Oct 14, 2008
    I'm wondering whether I really need to replace both the hot & cold lines. As I have outlined in other posts, my cold 3/4" is failing from pinholes.

    When I look at the pipes, the hot side is visibly in better condition -- not much green etc and looks smoother in general.

    So do I really need to replace the hot side as well?

    For that matter, the 1/2" cold lines look better than the 3/4" cold.

    Searching "pinhole leaks" etc on the Web finds several technical articles.

    "Although pinhole leaks could happen in any copper pipe or tube within a house, the Washington Suburban Sanitary Commission (WSSC) reported that the majority of pinhole leaks that their customers had reported were in cold-water, horizontal copper piping. Most of the leaks were in older homes, and 80 percent of the reports involved homes built prior to 1970."


    "Examine accessible/exposed copper piping for small, bluish-green stains on the pipes - away from joints. This can be an indication of a pinhole leak. Call a licensed plumber immediately at the first signs of leaks. (Bluish-green stains on copper pipes do not necessarily indicate there is a pinhole leak - they can appear on copper pipes in a damp environment, such as the basement.)"

    "The most widely publicized corrosion problems with copper plumbing [1,2,3,14] have occurred in treated and untreated water pumped from wells. Groundwater, as compared to surface water, is generally hard and alkaline, with a total dissolved solids content of 200 to 300 mg/l, or higher. Significant amounts of dissolved carbon dioxide are often present in groundwater, which if not properly treated, can be extremely aggressive to copper tube. The effect is most commonly referred to as Acold water pitting,@ and is characteristically observed in cold water plumbing, but not in hot. Pitting under these conditions is less sensitive to the effect of gravity, and as a rule, does not occur preferentially on the bottom of horizontal tubing, but rather, is distributed around the entire inside surface of the tube. Cold water pitting can be very aggressive, penetrating the tube wall in a relatively short time, but usually within three to four years after being placed in service. The frequency of leaks typically decreases after five years, and is rarely observed after 15 years or more.

    Pitting is almost always associated with hard well waters with pH values in the range from 7.0 to 8.2 [2]. NACE publication TPC No.7 [12] describes well waters having pitting tendencies are characterized by a pH of less than 7.8 and containing more than 17 milligram per liter (mg/l) of carbon dioxide. Well waters treated to raise the pH to 8.0, or above, to remove dissolved carbon dioxide are generally rendered non-corrosive to copper. Aeration is also an effective means of removing dissolved carbon dioxide, and has the added benefit of stripping dissolved hydrogen sulfide from the water, when present."


    "Green stains on porcelain fixtures are clear evidence of aggressive water "

    I see possibly contradictory advice on pH level.:
    "In copper pipe systems, when the pH is more than 8, a copper oxide film typically forms on the inside of the pipes and acts as a natural barrier coating. But if the pH drops to below 8, the barrier dissolves and the natural organic materials (NOMs) in the water will begin to corrode the pipe, resulting in pinhole leaks."


    Task Force Study - Final report on MD Task Force on pinhole leaks in copper pipes "Pinhole Leaks in Copper Plumbing."

    "5. Strive to minimize the aluminum in the processed water and to keep the pH below the EPA recommended maximum of 8.5.

    The presence of aluminum and high pH are factors that have been shown to increase the likelihood of pinhole corrosion in recent studies."


    "Your water pH should always be higher than 7."
  2. 99k

    99k Radon Contractor and Water Treatment

    Aug 16, 2008
    Contractor of Radon Reduction, Testing, and Water
    Fairfield Co.,Connecticut
    I have personally replaced many copper pipe sections in my house ... all cold water side. If the basement is easily accessible, I would only change out the sections that failed and address the acid problem ... there is no need to rip everything out. Before I fixed the ph level I could only keep a water heater for 3 years max before it leaked. No such problem anymore. What is the current ph level?
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  4. Cass

    Cass Plumber

    Nov 12, 2005
    In my area we had this problem in 1 area of a near by town...many homes were getting pin holes after 1-3 years of being turned out to be dielectric action originating from the ground outside of their home entering through the water line.
  5. jimbo

    jimbo Plumber

    Aug 31, 2004
    San Diego, CA
    Depends on the cause of the pinholes. But if any chemical reaction is involved ( ph, etc ) that action is usually accelerated by temperature, so it is not uncommon for leaks to occur more frequently on the hot pipes.
  6. msgale

    msgale Member

    Sep 28, 2006
    if it's dissolved carbon dioxide, then the water heater...

    will expel the CO2 as the water gets heated, so there is less co2 inheated water in the hot pipes, so less corrosion
  7. AcidWater

    AcidWater Member

    Oct 14, 2008
    But its a closed system-- where does the CO2 go? Warm carbonic acid would be slightly more corrosive...
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