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Undesirable Water FeatureChanges in the chemistry of municipal water supplies feeding our home plumbing systems can trigger potentially devastating pinhole leaks, like those shown here.Chuck Dolan

There has been chatter on my neighborhood-association listserv over the past eight years about pinhole leaks in copper household-water pipes. Several families have experienced them; others recounted horror stories about costly leaks that had suddenly plagued coworkers. What everyone has been asking is who’s at risk — and why?

As someone who’s been replacing old and rust-clogged galvanized basement pipes with copper over the past decade, these posts have riveted my attention. Marc Edwards of Virginia Tech now offers some insights into the problem. And they aren’t reassuring.

His research finds that the problem can sometimes trace to good intentions on the part of water companies. Others to infected pipes. Yes, we’re talking germs here.

As for who’s at risk, it’s anyone with copper piping. And the dismal news: Alleviating vulnerability is not something homeowners can likely undertake. Moreover, once a few leaks develop in some section of pipe, it becomes reasonable to expect they’re in the process of developing elsewhere. If they riddle pipes buried in a wall, replacing them might require tearing out scads of sheetrock. And if prophylactic repairs aren’t undertaken promptly, global leaks might emerge, damaging walls all over and spurring the growth of disease-fostering mold.

A study published earlier this year by a Virginia Tech team led by Ewa Kleczyk found that in Maryland household experiencing these leaks, costs to fix the problem ranged from roughly $1,300 to more than $18,000. Another Virginia Tech analysis headed by Eric Sarver, which was published at the same time, estimates that nationally the costs of preventing and coping with pinhole leaks conservatively runs some $928 million a year. Owners of single-family homes bear the brunt of the costs. Approximately half of their costs go for plumbing repairs, another third for labor charges, and the rest to cover property damaged by leaks.

In some instances, Edwards points out, “People have lost their homes” from pipe failures as insurers dropped families after the first sign of leaks — and later damage eclipsed the ability of homeowners to finance repairs.

When Edwards first contemplated the pinhole-leaks mystery, which was showing up in new and old pipes, he reasoned that it wasn’t the copper that had changed but instead the water that had become more corrosive. So his team spent a decade cooking up some 500 different water recipes. The chemists altered mineral constituents, pollutants, and of course pH.

Obviously, decreasing water’s pH — which means increasing its acidity — should threaten pipes. But the Virginia Tech engineers showed that raising the pH to between 8.5 and 9 (7 is neutral) and increasing chlorine concentrations in water proved a particularly devastating, if counterintuitive, combo. “With that recipe,” Edwards told me and a handful of other reporters touring his lab on Oct. 18 (as part of a Society of Environmental Journalists’ tour), “we were able to eat holes in a copper pipe in the lab. In just 11 months we got like six holes in a one-foot section of pipe.”

With these data, Edwards said, for the first time “we had definitive proof” that water utilities could be fostering the degradation of some home-plumbing systems. “This was the first time that anyone had ever reproduced [pinhole-leak formation] in the lab.”

He says that other contributing factors to a water-system’s leak-fostering potential can include:

 — removal of organic matter from municipally treated water, as now required by the Environmental Protection Agency. In the past, organic residues often collected on pipes’ interior surfaces, creating what turned out to be a somewhat protective coating 

— and a lining of water mains with cement to limit the likelihood that these community water-distribution conduits will corrode through, springing massive, gusher leaks. Because “the cement leaches a lot of lime into the water,” Edwards notes, “this treatment can raise water’s pH into the danger zone for pitting.”

Where might such conditions occur? Well, chlorine concentrations tend to be highest in water leaving a treatment plant. If the water travels far enough, it will lose that chlorine before entering a home. So communities nearest municipal treatment plants are especially vulnerable, Edwards says.

And the alkaline pH: Besides resulting from cement-lined mains, it can show up where utilities disinfect water by chloramination (a modern variation on the old theme of chlorination). The new treatment’s advantage is that it generates fewer potentially cancer-causing disinfection byproducts. And though chloramination doesn’t by itself raise a water’s pH, Edwards notes that many utilities deliberately raise pH to improve the quality of water that’s undergone this type of disinfection process.

The irony, of course, is that pipe pitting in these circumstances traces to good-faith efforts by the local utility to improve the healthiness of treated water. Edwards published some of these findings a few years ago based on studies funded by my local water utility (the Washington Suburban Sanitary Commission).

But the Virginia Tech team discovered that copper leaks can stem from other problems as well. For instance, pinhole-leak epidemics can emerge in some communities where the water’s chlorine concentrations are low.

Preliminary (and yet unpublished) findings by his team are now pointing in some of these instances to plumbing infections. They’ve extracted colonies of sulfate-reducing bacteria, also known as SRBs, from pits in the interior of copper pipes. These bugs emit hydrogen sulfide — the noxious and highly corrosive compound responsible for the smell of rotten eggs.

I’ve written in the past about how SRBs can munch right through tough metals, such as the stainless-steel pressure vessels in nuclear-power plants. Key to the bugs’ destructiveness is their acquiring a protective biofilm to isolate them from the oxygenated water.

You see, SRBs don’t thrive in the presence of oxygen. So they tend to emigrate to a metal surface and then invite other families of microbes to join their community. The newcomers build a protective outer layer, a biofilm, above the SRBs. This shield not only does a good job of barring the infiltration of oxygen, but also any germ killers that might later be seeded into the water.

Once a biofilm forms, SRBs are free to eat away at copper (or any other metallic meal) with impunity. At which point routing them becomes, well —  mighty challenging.

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