Unaccounted For Water

Unaccounted for Water A Real Drain on Your Water System
Unaccounted for water is a financial drain on a water utility. How much of a drain depends upon
the system. Utilities must constantly monitor and maintain their system and accounting
procedures to maintain an acceptable level of unaccounted for water. The apparent accepted
target for unaccounted for water across the nation is 10% to 12%. A suggested goal for
unaccounted for water is 5%. Unaccounted for water 40% or greater range is common. A private
industry would not operate at this level of inefficiency. Why should a publically owned utility?
Different elements contribute to unaccounted for water. These elements include leaks, inaccurate
meters, water consumed but not metered, improper meter reading and billing /accounting errors.
The following cases illustrate the financial drain caused by unaccounted for water.
Case I
System A, a small municipal water system, purchases water from another water system. System
A does not have an active meter change out program. There are loose accounting procedures in
respect to un-metered water use, incomplete leak detection surveys and a master supply meter of
early 1980's vintage.
Historically, System A had unaccounted water volumes 50 % to >70% of the purchased
volumes. The large percentage of water purchased but not sold caused System A to be in
constant financial distress. The system had increased the customer rates by modest amounts, but
these increases did not eliminate the financial woes of the system
System A had no choice but to address its problem. It started an aggressive meter change out
program, initiated a process to measure un-metered water use and worked on finding and
eliminating leaks. They also replaced the old master mechanical meter with a new meter.
These measures increased sales and reduced the unaccounted for water to 10% to 15% of the
purchased volumes. The revenue picture of System A improved dramatically. They are now
committed to continuous improvement, and to reducing unaccounted for water even more.
Case II
System B is a small municipal water system which needs a > 35 % customer rate increase to
break even. The city produces its own water and has an unaccounted for water rate of 30%.
They do not have an active meter change out program. If System B had implemented a plan to
manage unaccounted for water, it may have resulted in a smaller customer rate increase. System
B must now increase water rates and implement an unaccounted for water reduction plan to
remain solvent.
To manage unaccounted for water, a utility needs a master plan. The master plan must be
followed and updated on a regular basis. A good plan will include these elements:
1. Water audit with annual review.
2. Leak detection and repair strategy.
3. Meter change out program.

4. Annual meter testing on production and large use meters.
A water audit is a comprehensive study of the physical and paper side of the water system. It is
more in depth that a quick leak survey.
A leak in the system is the first item that most individuals think of when unaccounted for water
is mentioned. Leaks can go undetected for long periods of times due to proximity to sewer lines,
soil composition or stream crossings.
The utility must decide on whether to perform the water leak survey in-house or out source the
project. Leak detection equipment is costly and requires training and experience to consistently
obtain valid results. A leak survey of fire hydrants only is fairly quick and can obtain good
results. A more extensive survey includes all fire hydrants and as many gate valves as possible.1
An outside firm generally charges from $100 to >$500 per mile depending upon the situation.
The American Water Works Association (AWWA) gives guidance on preparing a Leak
Detection Survey. Review the specifics of your system prior to starting the survey. Specifics
include distribution composition, sizing, meter types, valve types and locations, blow-offs
locations, flushing information, etc.
Make a visual inspection by walking your distribution system, especially the parts in remote
locations. You may find problems which are hard to pick up otherwise.
Meters supply the data which generate revenue for your system. In other words, meters are the
cash registers for the utility. If the cash registers are not working properly then revenue is
lost. All meters age and lose accuracy over time.
Your meter program should include:
1. Production meters and large customer meters should be checked and certified on an
annual basis. Meters can either be removed and taken to a testing facility or checked in
place. It is best to check a meter in place, because the testing facility can not reproduce
the exact field operating conditions.
2. Have a meter replacement program. Your meter supplier will have an estimate of how
long his meter will work accurately. A ball park figure is 6 to 8 years or a million gallons.
3. Install production and large customer meters to meet flow (not pressure) requirements.
A large meter, properly installed in a pit and within operating tolerances (98 to 102% of
rated flow) will not record flow below its performance minium. This allows the customer
to receive water that he will not be billed because it is not recorded by the meter.
Unaccounted for water will always be a financial drain upon your water system. It is up to the
individual system to decide whether their drain will be the size of a 3/4 " pipe or a 36" main.
December 4, 2000
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Unaccounted for Water A Real Drain on Your Water System

3. Meter change out program.

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