evaluate its performance over a period of time by repeating the performance indicating tests and comparing them with previous results. Performance indicators and
benchmarks also allow comparisons between public water providers.
Accurate metering is crucial in a water loss control program. Metering establishes
production and customer use volumes as well as provides historic demand and
consumption data that is useful not only for auditing but for planning future needs.
There is no single type of meter that will accurately measure flow for all applications,
but there are a variety of meters that have been developed using different operating
principles, designed to perform within required tolerances under different circumstances. The cost of meters typically ranges from a few hundred dollars to thousands
of dollars per meter depending on size, complexity, and operating conditions. A
PWS must select the meters they use carefully according to intended use, flow rates,
and the environment where it will be installed. How the meters will be read is also a
decision that a PWS has to decide when considering metering programs. Meters can
be read manually but most PWSs are moving toward a variety of different Automatic
Meter Reading (AMR) systems that reduce reading errors and allow labor to be
reduced or reallocated.
While it is possible to spot losses through billing data discrepancies or abrupt
changes in amounts of water that have been historically used, it is typically necessary
to physically pinpoint the leak in the field. The location of a leak is not always
obvious unless it is large. An array of techniques and equipment are available to
assess leakage from distribution lines within a geographic area or pinpoint a leak
within a suspected segment of pipe. Flow monitoring of a District Meter Area
(DMA) can be used to determine leakage within an area that can be isolated and
may encompass 1500 to 2000 service connections. These techniques monitor flow to
specific areas and compare water flowing into the area with known or estimated night
usage to determine losses in the DMA or along a branch water line.
There are several different types of leak detection equipment that use different
operating principles. Acoustic equipment detects a leak through noise made by water
as it leaks from the pipe. Electromagnetic field detection is used on pre-stressed
concrete pipe and locates defective reinforcing steel in the pipe. Thermal detection
devices look for the temperature differences in the surrounding ground caused by
saturation due to the leaked water. Chemical detection relies on locating substances
added to the treated water such as chlorine or fluoride that do not occur naturally. A
tracer gas may also be introduced into dewatered lines. If there is a leak, a special
instrument can detect it at the surface. The different styles of leak detection equipment require varying levels of skill and experience to operate with accuracy. Capital
costs for typical leak detection equipment range from less than hundred to several
thousand dollars depending on its complexity.
Once a leak is located it should be repaired. Some repair techniques include
wrapping or using repair clamps. Replacement can be done by installing new pipe in
an excavated trench or by use of a trenchless method, such as sliplining or pipe
bursting, where a new pipe of the same size or larger is pulled through the existing
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N. K. Shammas et al.
benchmarks also allow comparisons between public water providers.
Accurate metering is crucial in a water loss control program. Metering establishes
production and customer use volumes as well as provides historic demand and
consumption data that is useful not only for auditing but for planning future needs.
There is no single type of meter that will accurately measure flow for all applications,
but there are a variety of meters that have been developed using different operating
principles, designed to perform within required tolerances under different circumstances. The cost of meters typically ranges from a few hundred dollars to thousands
of dollars per meter depending on size, complexity, and operating conditions. A
PWS must select the meters they use carefully according to intended use, flow rates,
and the environment where it will be installed. How the meters will be read is also a
decision that a PWS has to decide when considering metering programs. Meters can
be read manually but most PWSs are moving toward a variety of different Automatic
Meter Reading (AMR) systems that reduce reading errors and allow labor to be
reduced or reallocated.
While it is possible to spot losses through billing data discrepancies or abrupt
changes in amounts of water that have been historically used, it is typically necessary
to physically pinpoint the leak in the field. The location of a leak is not always
obvious unless it is large. An array of techniques and equipment are available to
assess leakage from distribution lines within a geographic area or pinpoint a leak
within a suspected segment of pipe. Flow monitoring of a District Meter Area
(DMA) can be used to determine leakage within an area that can be isolated and
may encompass 1500 to 2000 service connections. These techniques monitor flow to
specific areas and compare water flowing into the area with known or estimated night
usage to determine losses in the DMA or along a branch water line.
There are several different types of leak detection equipment that use different
operating principles. Acoustic equipment detects a leak through noise made by water
as it leaks from the pipe. Electromagnetic field detection is used on pre-stressed
concrete pipe and locates defective reinforcing steel in the pipe. Thermal detection
devices look for the temperature differences in the surrounding ground caused by
saturation due to the leaked water. Chemical detection relies on locating substances
added to the treated water such as chlorine or fluoride that do not occur naturally. A
tracer gas may also be introduced into dewatered lines. If there is a leak, a special
instrument can detect it at the surface. The different styles of leak detection equipment require varying levels of skill and experience to operate with accuracy. Capital
costs for typical leak detection equipment range from less than hundred to several
thousand dollars depending on its complexity.
Once a leak is located it should be repaired. Some repair techniques include
wrapping or using repair clamps. Replacement can be done by installing new pipe in
an excavated trench or by use of a trenchless method, such as sliplining or pipe
bursting, where a new pipe of the same size or larger is pulled through the existing
242
N. K. Shammas et al.