EPA scientists document, experiment, and research water chemistry to better understand the nature of pitting corrosion and pinhole leaks in copper water pipes.

Imagine a tiny, pinhead-sized hole in one of the copper water pipes running through the wall of your home. Water slowly drips, drips, drips. It soaks into the insulation and spreads until your wall becomes a breeding ground for mold and mildew that can not only make you sick, but can also go undetected for months or longer.

EPA researchers are gathering data and conducting experiments in an effort to get to the root of this aptly-named, “pinhole leak” problem. Pinhole leaks result from a localized copper corrosion called pitting corrosion, but the causes of this form of corrosion are poorly understood.

“Leaks from this corrosion can cause drywall damage, leaks on floors, mold build-up, and more,…but it’s a very, very complicated problem. It’s hard to predict and the mechanisms are difficult to sort out,” explains EPA environmental engineer Darren Lytle who has been involved with many of the pitting corrosion studies.

Since copper is a low-cost resource and allows for relatively easy installation, the majority of households across the country sit upon tunnels of copper plumbing. Not all copper plumbing experiences pitting corrosion, but often an entire community can be found where pinhole leak problems are prevalent. Researchers have been investigating what exactly separates such a community from the surrounding areas that are not experiencing similar corrosion problems.

“When there are widespread problems in a community, where many homeowners have a problem, it is likely associated with water chemistry,” says Lytle. “If we can understand what it is about the water chemistry that is in common among these communities, then we start to understand what water chemistries to avoid.”

“This is going to be something we have to follow and we have to watch,” warns Lytle. “It’s something we need be aware of as water becomes more scarce, as population grows, and as communities look to other sources with different chemistries to help supplement what they currently have. I think it’s a problem that is going to be around for awhile.”

Accordingly, researchers have been collecting water and pipe samples from both communities with pinhole leak problems and from nearby communities without. Using the data collected through these samples, as well as the documentation of full-scale case studies, researchers have compiled a database of corrosion distribution information and the associated water quality.

Using this information to compare problematic waters with corrosion-free waters will not only allow scientists to identify the mechanisms of pitting corrosion, but also to identify possible solutions to these problems. For example, one case study near Cincinnati, OH involved two neighboring communities, both receiving water from the same main source, but one community had prevalent pinhole leak problems while the other did not.

“We went to the community that doesn’t have a problem,” recalls Lytle, “and we found out the only difference is that they add a phosphate-based chemical for corrosion control, and the community that has a problem does not add phosphate.”

In addition to compiling this database and comparing water chemistries, researchers have designed and utilized a pipe-loop system to test water for its tendency to initiate pitting corrosion by continuously running water through a series of copper pipes. A small-scale, preliminary study using this pipe-loop system showed researchers that evidence of localized corrosion could be found after only 72 days of flowing water through the system. A tool like this pipe-loop system could prove very useful for water utilities.

“It’s an inexpensive system. You can go to the local hardware store and pick up all the plumbing and the fittings. A water utility could easily build it, put it in their water distribution system, and just run water through and periodically pull sections of the pipe out to examine them for any signs of corrosion by-products,” says Lytle, encouraging the use of such a system.

Pitting corrosion in copper piping is difficult for a homeowner to detect and correct before it becomes a big problem, and often will result in expensive repairs and replacement. The EPA-designed pipe-loop testing system offers the potential to provide a solution, giving water companies a low-cost early warning system for identifying water likely to lead to pinhole corrosion, and preventing homeowners from facing the damage and health risks that come from leaking pipes. Such pipe-loop testing systems could also help water companies to identify potential solutions for existing problems.

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