I WATER AUDITS AND WATER Loss CONTROL
United
Environmental Protection
FOR
This document provides an introduction to water loss control and information on the use of water audits
in identifying and controlling water losses in public water systems. Water audits are the first step in a
three-step process for controlling water loss. A water audit is followed by intervention to identify losses
and implement solutions and then by an evaluation of intervention measures and the needs for further
improvement. This document is intended for small and medium-sized water systems, as well as state
programs and technical assistance providers that regulate or support these systems.
Introduction
The Water Loss Problem
Public water systems face a number of challenges including aging infrastructure, increasing regulatory
requirements, water quantity and quality concerns and inadequate resources. These challenges may be
magnified by changes in population and local climate. It has been estimated that:
• The United States, will need to spend up to $200 billion dollars on water systems over the next
20 years to upgrade transmission and distribution systems.1
• Of this amount, $97 billion (29 percent) is estimated to be needed for water loss control."
• Average water loss in systems is 16 percent - up to 75 percent of that is recoverable."
A water loss control program can help water systems meet these challenges. Although it requires an
investment in time and financial resources, management of water loss can be cost-effective if properly
implemented. The time to recover the costs of water loss control is typically measured in days, weeks,
and months rather than years." A water loss control program will also help protect public health
through reduction in potential entry points for disease-causing pathogens.
Understanding Water Use and Water Loss
Much of the drinking water infrastructure in the United States has been in service for decades and can
be a significant source of water loss through leaks. In addition to leaks, water can be "lost" through
unauthorized consumption (theft), administrative errors, data handling errors, and metering
inaccuracies or failure. The International Water Association (IWA) and the American Water Works
Association (AWWA) have developed standard terminology and methods to assist water systems in
tracking water losses and in performing water audits. The standard terminology includes the terms
authorized consumption, real loss, apparent loss and non-revenue water that are used in this document.
• Authorized Consumption is water that is used by known customers of the water system.
Authorized consumption is the sum of billed authorized consumption and unbilled authorized
consumption and is a known quantity. It also includes water supplied to other water systems.
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Real Losses, also referred to as physical losses, are actual losses of water from the system and
consist of leakage from transmission and distribution mains, leakage and overflows from the
water system's storage tanks and leakage from service connections up to and including the
meter.
Apparent losses, also referred to as commercial losses, occur when water that should be
included as revenue generating water appears as a loss due to unauthorized actions or
calculation error. Apparent losses consist of unauthorized consumption, customer metering
inaccuracies, and systematic data handling errors in the meter reading and billing processes.
Non-Revenue Water (NRW) is water that is not billed and no payment is received. It can be
either authorized, or result from apparent and real losses. Unbilled Authorized Consumption is
a component of NRW and consists of unbilled metered consumption and unbilled un-metered
consumption.
What are the Benefits of a Water Loss Control Program?
A water loss control program helps to identify real or physical losses of water from the water system and
apparent losses, the water that is consumed but not accounted for. Real losses represent costs to a
water system through the additional energy and chemical usage required to treat the lost water.
Apparent losses represent a loss of revenue because the water is consumed but not accounted for and
thus not billed. Once a water system identifies these real and apparent losses through a water loss
control program, it can implement controls to reduce them. This can reduce the need for costly
upgrades and expansions due to population growth and increased demand. By reducing the amount of
water lost, the recovered water can be sold to consumers, generate revenue and meet water demands.
In some cases this can reduce the need to find additional sources. Water loss control programs are often
the most economical solution to increasing demand, especially in the short term.'
What Does a Water Loss Control Program Look Like?
A water loss control program consists of
three major steps (see Figure 1). The critical
first step is the water audit. A water audit
identifies and quantifies the water uses and
losses from a water system. The intervention
process addresses the findings of the water
audit through implementation of controls to
reduce or eliminate water losses. The
evaluation step uses performance indicators
to determine the success of the chosen
intervention actions. Utilizing the standard
terminology and the three steps of a water
loss control program, systems can determine
their baseline water use and loss, prioritize
and implement water efficiency projects and
operational changes, and evaluate and
continuously improve their water loss
Figure 1. Components of a Water Loss Control
Program
Water Audit
Evaluation
Intervention
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management.
Figure 2 provides a summary of the main data needs, action items and performance indicators for each
step of a water loss control program. The following sections will go into more detail for each step.
Step 1 - Water Audit Data
Needs
Step 2- Intervention
Action Items
• Gathering information.
• Determining flows into and
out of the distribution
system based on estimates
or metering.
• Calculating the
performance indicators.
•Assessing where water
losses appear to be
occurring based on available
metering and estimates.
•Analyzing data gaps.
• Considering options and
making economic and
benefit comparisons of
potential actions.
• Selecting the appropriate
interventions.
• Gathering further
information, if necessary.
• Metering assessment,
testing, or a metering
replacement program.
• Detecting and locating
leaks.
• Repairing or replacing pipe.
• Operation and maintenance
programs and changes.
•Administrative processes or
policy changes.
• No further action is
necessary.
Step 3 - Evaluation
Performance Indicators
•Were the goals of the
intervention met? If not,
why not?
•Where does the system
need more information?
• How often should the
system repeat the audit,
intervention and evaluation
process?
• Is there another
performance indicator the
system should consider?
• How does the system
compare to the last audit,
intervention and evaluation
process?
• How can the system
improve performance?
Figure 2. Summary of Data Needs, Action Items, and Performance Indicators of a Water Loss Program
The Importance of Metering
Water meters, both at the source and the service connection, are very important for all aspects of the
water supply operations and make accurate water auditing possible. They make it possible to charge
customers based upon the quantities of water that the customers consume. They record usage and
make billing fair for all customers. They can encourage conservation by making customers aware of their
usage as well as help detect leaks and establish accountability. Meter records provide historic demand
and customer use data that is used for planning purposes to determine future needs. Unmetered water
systems will need to consider some level of system metering to address water loss in the system.
A variety of meters exist and each type has its advantages and disadvantages. There is no single type of
meter that will accurately measure flow for all applications. To select the proper meter for a specific
application, a variety of factors should be considered in order for the meter to satisfy the location
requirements and conditions where it will be installed. More information about the types and
applications of meters can be found in EPA's Control and Mitigation of Drinking Water Losses in
Distribution Systems, EPA 816-R-10-019, November 2010. The document is available at:
http://water.epa.gov/type/drink/pws/smallsvstems/technical help.cfm.
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Step 1 - How to Complete a Water Audit
A water audit is an accounting of all of the water in a water system resulting in a quantified
understanding of the integrity of the water system and its operation. It is the first step in formulating an
economically sound plan to address water losses. A preliminary water audit begins with the following
information and simple calculations :'
1. Determine the amount of water added to the system, typically for a one year period,
2. Determine authorized consumption (billed + unbilled), and
3. Calculate water losses (water losses = system input - authorized consumption)
a. Estimate apparent losses (unauthorized consumption + customer meter inaccuracies +
billing errors and adjustments)
b. Calculate real losses (real losses = water losses - apparent losses)
These steps are an example of a top down audit, which starts at the "top" with existing information and
records. It may also be known as a desktop audit or paper audit since no additional field work is
required. Water systems are dynamic. The water audit process and calculation of the water balance,
when routinely performed, is a useful guide for a system's water loss control program. Water systems
can get started using the data that is readily available, identify any data gaps and then work towards
improving their data.
After performing an initial top down audit it may become evident that some of the numbers are rough
estimates. The next action in the audit process is to improve any initial estimates and begin reducing
non-revenue water losses. A bottom up audit is often implemented after several top down audits have
been completed and can better quantify loss volumes that were not revealed by the top down audit. A
bottom up audit will help find apparent and real losses and begins by looking at components or discrete
areas in the utility's operations. A bottom up audit assesses and verifies the accuracy of the water loss
data associated with individual components of the water system. A bottom up audit could include
estimates of water used in municipal operations such as fire fighting, distribution system flushing and
street cleaning, as well as metering of all authorized uses.1"
Bottom up audits are more costly since they are more labor and staff intensive. The top down audit can
help to identify areas where bottom up audit efforts should be concentrated. There are several
techniques and methods used to perform a bottom up analysis. They are described in detail in Control
and Mitigation of Drinking Water Losses in Distribution Systems, EPA 816-R-10-019, November 2010,
which can be found at: http://water.epa.gov/type/drink/pws/smallsvstems/technical help.cfm.
Additional data often needs to be collected to perform a water audit. Additional data collection can
occur during the audit or intervention phase and may include the following:'
• Locating leaks and losses can be accomplished through an examination of billing records, flow
monitoring, visual inspection or leak detection equipment (e.g., acoustic, thermal,
electromagnetic, tracer). Through an examination of billing records, a water system may identify
sudden changes in water usage at particular locations in the water system, which could indicate
the need to investigate further for possible leaks or theft. Flow monitoring can be conducted by
examining individual customer meter records, metered districts or through placement of
temporary meters in suspect locations. These temporary meters clamp onto pipes and do not
sacrifice the integrity of the pipelines.
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• Condition assessment tools include traditional external visual inspections (e.g., periodic walk-
over and opportunistic inspections of exposed mains), internal visual inspection technologies
(e.g., closed circuit television (CCTV) camera inspections), pit depth measurements, destructive
testing (e.g., test coupons) and non-destructive testing (e.g., ultrasonic testing).
• Hydraulic modeling can be used to predict locations of leaks in a water system based on
physical and operating data of the water system. Calibration of these models to actual field data
is essential to obtain realistic and usable results.
Water Audit Resources
*~ AWWA provides Free Water Audit Software©, available at:
http://www.awwa.org/Resources
*~ Georgia Department of Natural Resources, Georgia Water System Audits and Water Loss
Control Manual, Version 1.0 (2011), available at:
http://www.gaepd.org/Files PDF/GaWaterLossManual.pdf.
*~ The Maryland Department of the Environment's Developing and Implementing a Water
Conservation Plan, includes water audit worksheets and describes the development of a
water conservation plan. The information is available at:
http://www.mde.state.md.us/programs/Water/WaterConservation/Documents/www.mde.
state.md.us/assets/document/water cons/WCP Guidance2003.pdf.
*~ The Texas Water Development Board's Water Loss Audit Manual (2008) includes a water
audit worksheet. The manual and worksheets are available at:
http://www.twdb.state.tx.us/conservation/municipal/waterloss/.
*~ The New Mexico Office of the State Engineer provides examples of water audits of public
water systems using the IWA/AWWA process. Information is available at:
http://www.ose.state.nm.us/wucp accounting.html.
Step 2 - The Intervention Phase
Interventions are actions taken by a water system to identify the specific sources of water loss and
implement solutions. These actions can include:'
• Preventive measures such as design standards and effective maintenance
o Reliable construction and design standards allow a water system to maintain maximum
structural integrity throughout its operating life. Once a water system has been
constructed according to appropriate design standards, effective maintenance can help
to ensure the system operates at optimal performance throughout its lifespan and
ensure that repairs are made proactively.
• Meter installation, testing and replacement
o Accurate metering is important for all phases of a water audit. Meters record usage and
monitor demand, encourage conservation, help detect leaks and make it possible to
charge customers for the water they use.
• Leakage management
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o Detecting, pinpointing and repairing leaks generates event data that refines and
confirms the water losses identified in the water audit.
o Pressure management evaluates areas of excessive pressure and implements controls
that reduce pressure to cut pressure-sensitive background leakage and reduce rupture
rates.
• Pipe repair and replacement
o Once a leak has been detected and located, the pipe can be repaired or replaced.
Repairing and replacing pipes requires trained personnel, the right tools and the proper
inventory of parts and materials.
Step 3 - The Evaluation Phase
The evaluation phase is important for ensuring an efficient and effective water loss control program.
Comparison of the water system to industry benchmarks or past audits can document improvements in
water loss control and allow a water system to track its progress. Use of performance indicators such as
those mentioned above can help to ensure meaningful interpretations of the evaluation and to
encourage continuous improvement. The evaluation will answer questions such as:
• Were the goals of the intervention met? If not, why not?
• Where do we need more information?
• How often should we repeat the Audit, Intervention and Evaluation process?
• Is there another performance indicator we should consider?
• How did we compare to the last Audit, Intervention and Evaluation process?
• How can we improve performance?
Benchmarking for Small Systems
Conducting a water audit allows a system to monitor its water loss performance over time and compare
itself to other systems. This process is known as benchmarking and uses a collection of performance
indicators to numerically evaluate different aspects of the water system. Performance indicators need
to be consistent, repeatable and presented in meaningful standardized units. Some examples are
breaks per mile of distribution main per year, gallons of water lost per service connection, and gallons of
leakage per mile of distribution main per year. Because conditions at small systems can vary so greatly,
benchmarking can become a difficult practice as many performance indicators may not be consistent or
comparable across small systems. However, the basic steps of top-down water audits, metering and
water loss control efforts can help small systems conserve their resources and improve their long term
sustainability.
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Resources
Performing a water audit and developing a complete water loss control program does not have to be
overwhelming. By beginning with the basic steps and principles outlined in this document, any water
system can begin the process of identifying and mitigating water losses. Additional resources available
to assist water systems in performing water audits include the following:
*~ EPA Office of Ground Water and Drinking Water, http://www.epa.gov/drink/
*~ EPA Office of Water, Water Infrastructure: Moving Toward Sustainability.
http://water.epa.gov/infrastructure/sustain/index.cfm
*~ Association of State Drinking Water Administrators, http://www.asdwa.org
*~ The Alliance for Water Efficiency . http://www.allianceforwaterefficiency.org
*~ American Water Works Association, http://www.awwa.org
Resources are also available to assist water system customers in conducting a water audit of their
premises. These resources include the following:
*~ The Maryland Department of the Environment provides instructions on how to conduct a home
water audit as well as a spreadsheet that calculates current use using customer entries.
http://www.mde.state.md.us/programs/Water/WaterConservation/WaterAuditing/Pages/Progr
ams/WaterPrograms/Water Conservation/Water Auditing/index.aspx
*~ Broward County Florida Water Services provides a worksheet for plumbing fixtures and
appliances to calculate residential water use and provides average use for comparison.
http://www.cob.org/documents/pw/environment/water-conservation/home-water-audit-
worksheet.pdf
*~ The City of Corvallis, Oregon, Utilities Division provides information for residential customers on
checking for leaks using the water meter, measuring or estimating flows in plumbing fixtures
and measuring water used in landscaper irrigation.
http://www.ci.corvallis.or.us/index.php?option=content&task=view&id=443<emid=384
1 U.S. Environmental Protection Agency. 2009. Drinking Water Infrastructure Needs Survey Fact Sheet, EPA 816-F-
09-003. http://water.epa.gov/infrastructure/drinkingwater/dwns/factsheet.cfm.
" Thornton, J., Sturm, R., Kunkel, G., Water Loss Control Manual (2nd Edition), McGraw-Hill, 2008.
'"Texas Water Development Board, Water Conservation Task Force, Water Conservation Best Management
Practices Guide, November 2004. http://savetexaswater.org/bmp/.
Office of Water (4606M) EPA 816-F-13-002 July 2013
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