Water Main Break Study Released

June 2012, Vol. 67 No. 6
Houston water main crews dealing with a line break during the 2011 drought.

The Comprehensive Water Main Break Rate Study for the United States and Canada compiles the collective experience of 188 utilities which can be used for making future critical pipe replacement decisions. Highlights of the Comprehensive Water Main Break Study include a new national metric for citizens served per one mile of pipe, aggregate data on pipe material break rates, analysis of age and corrosion in failure modes, and related observations on pressure, temperature and trenchless technology practices.

During 2011, Utah State University conducted a study of utilities across the United States and Canada to obtain data on water main failures of municipal and private water supply systems. The study was comprised of two parts: a basic survey and a more detailed survey. The focus of the basic survey was to examine the number of failures utilities were experiencing and how those failures related to the pipe materials used. This effort focused on water supply mains (sewer and force main pipes were excluded). A variety of pipe materials are used in water supply systems and over the past 100 years the materials have evolved with different manufacturing technologies. As a result, pipe performance has changed. A goal of the more detailed level of analysis was to look at which materials were performing best at a snapshot in time and to track how pipe age affects failure rates.

The study found that most utilities use several kinds of pipe materials with 80 percent of the installed water mains utilizing a combination of cast iron (CI) at 28 percent, ductile iron (DI) at 28 percent and PVC pipe at 23 percent. This fact is supported by a relative low amount (13 percent) of utilities which avoid DI due to corrosion concerns.

Water main pipe material usage varies significantly over geographic regions. The Northeast and North Central region of the U.S. use either CI or DI pipe for approximately 90 percent of its length. In Canada, PVC pipe makes up 43 percent of the total.

The study concluded that the water main break experiences of one utility may not represent another. Factors such as climate, installation practices and soil corrosivity can greatly affect failure rates. Every utility should properly install pipe, regardless of material used.

When failures rates of cast iron, ductile iron, PVC, concrete, steel and asbestos cement pipes were compared, PVC is shown to have the lowest overall failure rate according to the report.

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