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Plumbing Engineer - Columns: April 2012: Designer's Guide

That old leaky feeling and copper pipe corrosion

By Timothy Allinson, P.E.,
Murray Co., Long Beach, Calif.

Just before Thanksgiving, six months after I moved into my current home, I experienced my first slab leak. For those unfamiliar with the term, this refers to homes in warm climates without basements that have a portion of their water piping installed below the grade slab. When one of these pipes springs a leak, it is referred to as a slab leak, because the water comes up through the slab. These leaks are, unfortunately, quite common in So Cal and, just as unfortunate, expensive to fix.

Since I sit on the board of two homeowners associations, I am all too familiar with the frequency of slab leaks and pinhole pipe leaks that occur several times a month in these two So Cal communities. For this reason, a local news headline that read, “Homebuilders Sue Water Districts over Pipe Leaks” caught my attention. It seems that two large local homebuilders, Shapell Industries and Lennar Homes, are suing the Moulton Niguel Water District (MNWD), Metropolitan Water District (MWD), and Santa Margarita Water District (SMWD) for using chloramines to disinfect their water supply, with the claim that the chloramines are destroying the copper water pipe in the homes they build.

The reason this subject interests me so much is not just because of my personal stake in my home and its piping but the increasing acceptance and use of plastic piping products in the plumbing industry, and the fact that plastics are less subject to damage from the treatment chemistry of water purveyors than copper is.

This is not a new subject. For whatever reason, it received a lot of attention in 2005 – 2006; since then, the subject seems to have gone dormant — until now.

In June 2005, Builder Magazine reported that the California Professional Association of Specialty Contractors (CalPASC) alleged that chloramine use in California was causing pinhole leaks in copper pipes. Their goal was to get the state of California to stop its code restriction against the use of plastic piping products, which it has done recently.

The EPA, as a response to Builder’s inquiry, has stated that it does not have an official position on the use of plastic versus copper pipe but noted that leaks in copper pipe can be the result of excessive water corrosivity, and that water utilities should adjust the chemistry of their water accordingly. Has that happened? It would not seem so. The EPA has noted recently that any utility considering the use of chloramines “should determine whether or not it has the resources to properly maintain and monitor its water quality so that these issues do not become problems.”

So, what are safe chloramines levels for copper pipe? The debate on that is far reaching and, sadly, inconclusive. There are so many variables that affect the corrosion process that it seems impossible to point to a single solution. The EPA’s standard is a maximum of 4 ppm (or mg/L). In contrast, investigations done at the Willmar, Minn., water treatment plant (Murphy, O’Connor and O’Connor) suggest that chloramines should be limited to 1 ppm to protect household plumbing. However, this same report also notes that the absence of disinfectant residual can permit the colonization of microorganisms that accelerate copper corrosion rates. So, clearly, the use of chloramines is a balancing act.

The studies done on chloramines and copper pitting are voluminous and inconclusive. The subject of a master’s thesis by Caroline Nguyen for Virginia Polytech in 2005 was 96 pages in length and said little more than, “further work is required in this area.”

The NAHB Research Center (National Association of Home Builders via gave a partial list of studies done on the source of pinhole leaks in 2006. Causes ranged as follows: combinations of pH, organic matter, aluminum solids and chlorine reported by Virginia Tech in 2004; aggressive water, poor workmanship and water softeners reported by University of Florida in 1997; excessive use of flux, reported by the AWWA in 1996; aluminum-bearing compounds reported by a Maryland task force; myriad combinations of water quality and system maintenance, but no mention of chloramines reported by the AWWA in 2001; chloramines, specifically, reported by Virginia Tech in 2004 (which contradicts their other report on the same subject in the same month and year) and design problems such as pipe sizing and velocity reported by Lewis Engineering and Consulting Inc.

It is very hard to determine the real source of leaks in copper pipe because of the time it takes for the leaks to occur, combined with variations in water velocity and water chemistry. It is claimed that chloramines themselves do not cause corrosion, except in combination with aluminum, but sources such as Citizens Concerned About Chloramines (CCAC) in San Francisco, as well as the EPA, make claims that chloramines will cause pinhole leaks purely by the nitrification they create, which lowers pH and causes pinhole leaks. Nitrification itself carries a host of other problems, such as loss of disinfectant residual and myriad health effects.

Another complicating factor in this debate is that many of the problematic leaks, at least here in So Cal, are the aforementioned slab leaks. While above-grade pinhole leaks can be sampled and studied, slab leaks are typically abandoned below grade and piping rerouted. As such, the leak source cannot be studied. A slab leak might be caused by a pinhole leak, or it might be caused by a cracked fitting or puncture from a rock due to building settlement. There is no practical way of knowing the cause.

In my opinion, as well as that of the CCAC’s, water utilities should be banned from using chloramines until more accurate studies can be performed to determine a safe method for their use. Until such time, a combination of filtration and traditional chlorine would better safeguard our health and copper piping. It would seem in the interest of the Copper Development Association (CDA) to lobby for this change. Perhaps they already are, but if this does not occur, the water utilities are pushing the industry toward increased use of plastics. I personally wish my home were piped in plastic rather than copper. If so, I wouldn’t have to turn my water off every time I leave the house for a day or more, due to lack of confidence in the copper piping.

What angers me the most is attitudes in response to the Shapell Industries’ $5 million claim. “If the water was to blame [for the pinhole leaks], the problem would be more widespread.” The problem is so widespread that it is driving change in our industry and our codes. All you need is Internet access in order to figure that out.

If Shappell and Lennar win their lawsuits (which they probably won’t, due to great pressure to the contrary), there will be a plethora of ensuing lawsuits to the same effect. This, of course, will benefit no one except the attorneys. We, the water consumers and taxpayers, will just end up paying the damages. Because, after all, we can’t stop consuming water, can we?

Timothy Allinson is a senior professional engineer with Murray Co., Mechanical Contractors, in Long Beach, Calif. He holds a bsme from Tufts University and an mba from New York University. He is a professional engineer licensed in both mechanical and fire protection engineering in various states, and is a leed accredited professional. Allinson is a past-president of aspe, both the New York and Orange County Chapters. He can be reached at

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