|Pipes and Public Health|
WATER MAIN BREAKS RATES IN THE USA AND CANADA - Utah University
Quality drinking water brought to the tap through elaborate underground
distribution systems is a critical component to our public health and economic well-being.This study published by Utah University in April 2012 offers an interesting overview of underground pipes in the USA and Canada, their age, size and failure rate by material type. Here are some of the highlights:
In the United States and Canada, underground water infrastructure was installed during three main time periods
because of the population growth in the 1800s, 1900-1945, and post 1945. Pipes constructed in each of these three
eras will all start to fail at nearly the same time over the next couple of decades for a number of reasons ranging
from age and corrosion to inadequate design and poor installation.
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Over 54,000 community water systems face the inevitable cost of pipe repair and replacement. The United States
EPA states that nearly 60% of the total system costs are found in the distribution and transmission pipe lines.
A total of 117,603 miles of pipe were reported by the 188 survey participants. This represents approximately
10% of the total length of water mains in the USA. This is one of the largest surveys conducted on water mains
failures and the results give an accurate representation water main behavior in the USA and Canada.
Nationwide One Mile of Installed Water Main Serves 264 People
While in urban areas the industry has assumed 325 people are served for 1 mile of distribution system pipe,
this survey suggests a new national metric of 264 people served per 1 mile of pipe regardless of utility size.
Also, 66% of all water mains are 8" or less in diameter and the range of 10" to 14" make up another 18% of all
installed water mains.
Most Utilities Use Several Kinds of Pipe Materials
80% of the installed water mains utilize a combination of Cast Iron (CI) at 28%, Ductile Iron (DI) at 28% and PVC
pipe at 23%. This fact is supported by a relative low amount (13%) of utilities which avoid DI due to corrosion
Pipe Material Use Differs by Region
Water main pipe material usage varies significantly over geographic regions. The Northeast
and North Central region of the USA uses either CI or DI pipe for
approximately 90% of its length. In Region 9, Canada, PVC pipe makes up 43% of the total.
There is Considerable Scatter in Pipe Failure Rate Data
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. In order to have an accurate water main break survey, a large number of respondents are required.
PVC Pipe Has the Lowest Overall Failure Rate
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.
Corrosion is a Major Cause of Water Main Breaks
75% of all utilities have corrosive soil conditions and combined with a high portion of CI and DI pipes, one in
four main breaks is caused by corrosion which is ranked the second highest reason for water main pipe failure.
The Average Age of Failing Water Mains is 47 years old
43% of water mains are between 20 and 50 years old and 22% of all mains are over 50 years old. While pipe
life can be estimated at over 100 years, actual life is affected by soil corrosivity and installation practices. Based
on the detailed survey, the average expected life of pipe being put in the ground today is 79 years. For example,
non-corrosive materials like PVC have an estimated life over 110 years. Regardless of the pipe
material selected, installation practices will affect the actual life that can be achieved.
The Average Supply Pressure is 77 psi with Pressure Fluctuations less than 20 psi.
Pressure events can contribute to water main breaks for pipes that have internal corrosion (tuberculation) or
weakened areas due to external corrosion. Pressure is an important component to pipe design and material
selection. A well-controlled system operated below design limits will lead to extended pipe life.
The Use of Trenchless Technologies will continue to Increase
While 57% of utilities use some form of leak detection, fewer utilities have engaged in trenchless technologies
like pipe relining, pipe bursting and directional drilling. Over 40% are considering pipe relining and pipe bursting
in the future. Directional drilling is more widely accepted and has a higher satisfaction rating and as a result,
74% of utilities are considering it in the future.
Over 8% of Installed Water Mains are Beyond Their Useful Life
This figure corresponds well with an EPA study (EPA, 2002) that shows the amount of pipe needing immediate
replacement is growing rapidly. Improved asset management will be essential to all utilities to survive this trend.
SOURCE: Water Main Break Rates in the USA and Canada: A Comprehensive Study - April 2012 Utah State University Buried Structures Laboratory | Steven Folkman, Ph.D., P.E.
All Rights Reserved - 2012 - Water Chronicles Inc.