Jan2012_ES&E_D6_ES&E 12-02-02 11:00 PM Page 67
Water Systems
Acoustic-based pipe assessment technology
reduces water leakage rates
By Marc Bracken
The correlator interface indicates the effective wall thickness of the surveyed span of asbestos cement pipe as well as
any existing leaks to engineers. Leaks are detected within 1”-3”ft of accuracy.
A
ccording to the US Environmental Protection Agency,
some 700 water main breaks
occur every day in the United
States and Canada, amounting to approximately 250,000 breaks each year. Also,
EPA estimates that, on average, 14 percent of treated water is lost to leaks.
The District of Maple Ridge, British
Columbia, provides drinking water to
more than 68,000 residential and commercial customers through 380 kilometres of water mains. Located 26 miles east
of Vancouver on the north bank of the
Fraser River, the District was experiencing leaks and main breaks in sections of
its water system, which is comprised
mainly of ductile iron pipe. However, approximately 18% of its water system is
comprised of asbestos cement and cast
iron, and most of the leaks and breaks are
experienced in these areas.
Normally, Maple Ridge would analyze
the break histories of parts of its water
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system to determine which sections
needed to be prioritized for replacement.
However, it began searching for a solution
that would help support this approach by
non-invasively measuring the effective
wall thickness of selected water pipes as
a means of better anticipating what sections were most vulnerable to future
breaks.
Maple Ridge turned for help to Echologics LLC, a developer of advanced
acoustic-based technologies for water
loss management, leak detection, and
pipe condition assessment. A subsidiary
of Mueller Water Products, Inc., Echologics works with municipalities worldwide to isolate “silent” leaks that
traditional leak detection and condition
Normally, Maple Ridge would analyze the break histories
of parts of its water system to determine which sections
needed to be prioritized for replacement.
“Maple Ridge is a growing community with a fairly young infrastructure,”
said Ed Mitchell, Maple Ridge’s Waterworks Superintendent. “Except for 42
miles of asbestos cement and cast-iron
pipes with some ductile iron, we’re in
good condition. Our main driver in investigation and replacement was trying to
determine a pipe’s remaining useful life.”
assessment methodologies fail to find. Its
proprietary sensor and signal conditioning technologies substantially reduce
both electronic “white” noise as well as
ambient background noise often created
by running water, traffic or pumps. It
works well on all pipes regardless of diameter, geometry, material, etc.
Data collection is non-invasive, using
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Jan2012_ES&E_D6_ES&E 12-02-02 11:00 PM Page 68
Water Systems
standard pipe appurtenances such as hydrants, valves, or direct attachments to the
pipe’s outer wall. The system also has the
ability to assess the structural condition of
transmission mains and distribution
pipelines, including a unique solution for
asbestos cement pipe.
Mitchell wanted to gauge the accuracy
of the company’s condition assessment
capabilities. Therefore, the District had
Echologics assess the condition of two
sections of 6-in. asbestos cement pipe in
its system, which it already knew was
badly degraded.
In order to conduct the acoustic-based
surveys, engineers placed two hydrophones on valves and fire hydrants that
were connected to selected sections of the
system. Once the hydrophones were in
place, a correlator listened for variations
of acoustic signals that were introduced
into the pipes by flowing water from hydrants, physically tapping on appurtenances such as valves, or by attaching
vibro-mechanical shakers to the system.
Changes in the acoustic signals enabled
engineers to accurately measure wall
thickness of the pipes, while simultaneously pinpointing leaks without breaking
Matthew Coleman, senior field specialist for Echologics, listens as acoustic
signals are induced into a section of asbestos cement pipe through a hydrant
using LeakFinderRT.
ground or disrupting service.
Once Echologics had surveyed both
sections of pipe, Maple Ridge compared
unearthed samples of the pipes to the
condition assessment report provided.
The results were found to be nearly identical. The company’s findings accurately
indicated that both pipes had remaining
wall thicknesses of 7.7 mm, which meant
that the pipes were significantly degraded. They had lost more than half
(-54.2%) of their original wall thickness.
The ability to accurately and non-invasively locate leaks and assess the wall
thickness of pipes is a result of LeakfinderRT, a Windows-based leak detection
and pipe condition assessment system. Its
ability to accurately detect leaks on asbestos cement and metallic pipes is a result of an enhanced correlation function,
which dramatically improves its ability to
accurately identify and locate narrowband leak noise. This capability is ideal
for plastic pipes, multiple leak situations,
and scenarios where there is a large
amount of background noise, or where
leak sensors have to be closely spaced.
Maple Ridge now uses results from
Echologics’ leak detection and pipe condition assessments, along with its pipe
breakage histories, to help prioritize repairs and replacement of its water system.
A pattern of break reductions has been
established for the District. In 2010, there
were a total of six breakages in the system. In 2011, there were only two.
Marc Bracken is with Echologics.
For more information, E-mail:
[email protected]
68 | January 2012
Environmental Science & Engineering Magazine