Apparent and Real Losses
Two broad types of losses occur in drinking water utilities:
Apparent losses are the non-physical losses that occur in utility operations due to customer meter inaccuracies,
systematic data handling errors in customer billing systems and unauthorized consumption. In other words, this
is water that is consumed but is not properly measured, accounted or paid for. These losses cost utilities revenue
and distort data on customer consumption patterns.
Real losses are the physical losses of water from the distribution system, including leakage and storage
overflows. These losses inflate the water utility's production costs and stress water resources since they
represent water that is extracted and treated, yet never reaches beneficial use.
Are these losses the same as 'unaccounted-for' water?
Research has found that past practices of defining and calculating "unaccounted-for" and the "unaccounted-for
percentage" varied so widely in utilities around the world that these terms had no consistent
meaning. Additionally, the "unaccounted-for percentage" indicator is mathematically misleading and reveals
nothing about water volumes and costs, the two most important factors in water efficiency assessments.
The IWA/AWWA Water Audit Method holds that all water supplied by water utilities can be accounted for, via
metering or estimation, as either a form of consumption or a loss. Hence no water is "unaccounted for." In its
2003 Committee Report, and in AWWA M36 Water Audits and Loss Control Programs, Third Edition, the
AWWA Water Loss Control Committee recommends against the use of the imprecise term "unaccounted-for"
water or unaccounted-for percentage, referring instead to the specifically defined term non-revenue water
included in the IWA/AWWA Water Audit Method .
What are the best ways for water utilities to control their apparent losses (customer meter
inaccuracy, systematic data handling error & unauthorized consumption)?
Providing quality drinking water is a critical service that generates revenues for water utilities to sustain their
operations. But these revenues rely upon efficient systems of customer metering, meter reading, billing and
enforcement that prevent consumption data error - and revenue loss - from occurring. Water utility managers
can address these losses by first assessing their policies and mapping the workings of the customer billing
system.
Do policy loopholes exist that allow water to be taken without the knowledge and authorization of the utility?
Do all customers exist with an account in the customer billing system (whether or not the system is metered)?
Are customer meters replaced before they lose accuracy from wear? Is meter reading accurate and complete?
Taking time to compile a flow chart of current activities and comparing them to the expectations for revenue
recovery usually uncovers a number of shortcomings that can be corrected to recover lost water and
revenue. Often these corrections require inexpensive procedural or programming changes that can recoup
considerable uncaptured revenue and successfully launch a water loss control program.
Water Loss Control: Apparent and Real Losses
Copyright© 2012 American Water Works Association
Rapidly advancing technology in Automatic Meter Reading (AMR) Systems and Automated Metering
Infrastructure (AMI) offers outstanding capabilities to water utilities to improve their efficiency in capturing
customer consumption data, identifying wasteful usage and leakage, and other enhancements to improve
revenue capture and manage water and revenue losses.
What are the best ways for water utilities to control their real losses (leakage, storage
overflows)?
Many drinking water utilities around the world respond to leaks only after they have received a report of water
erupting from a street or a complaint from a customer about a damp basement. Utilities that employ this type of
reactive leakage response most likely have excessive leakage that will never be reliably contained.
Controlling leakage effectively relies upon a proactive leakage management program that includes a means to
identify hidden leaks, optimize repair functions, manage excessive water pressure levels, and upgrade piping
infrastructure before its useful life ends.
Effective technologies have been developed in recent years including flow and component analysis to quantify
leakage amounts, leak noise correlators and loggers to pinpoint leaks, and pressure management to
systematically reduce leakage under the right conditions. Many effective strategies now exist to allow water
utilities to identify, measure, reduce or eliminate leaks in a manner that is consistent with their cost of doing
business.
Water Loss Control: Apparent and Real Losses
Copyright© 2012 American Water Works Association