Water loss from a water distribution system is a significant factor affecting water delivery to customers. Water loss can be either: (a) the apparent losses because of meter inaccuracies or unauthorized consumption or (b) real losses because of leakage at water service lines, breaks or leakage on mains and hydrants/laterals or at storage facilities. By using loss prevention methods such as the new International Water Association (IWA) Performance Indicator Methods, or other standard methods, Louisiana communities will be able to promote a more thorough assessment of water loss among water utilities.

BASIC DATA AND INFRASTRUCTURE REQUIREMENTS

Awareness that water loss is occurring in a water system is the first step in identifying leaks and making repairs. Once water loss has been documented and identified, a water system operator can then determine whether the water loss is a real loss or an unavoidable loss. The first step in accounting for water used and lost in a water distribution system is appropriate data collection, especially from water meters.

Important data needed to assess water use and loss in a system include:

A) Information relating to the water system infrastructure:

• production water meters (quantity, age, diameter, type, location, accuracy)
• water mains (age, material, diameter, length, location, depth, condition)
• water service lines (quantity, material, diameter, location, depth, length)
• valves (quantity, age, diameter, type, location)
• fire hydrants (quantity, age, type, location)
• customer water meters (quantity, age, diameter, type, location, accuracy)
• storage reservoirs (volume, location, type)
• bulk metering of water imported and water exported (quantity, age, diameter, type, location, accuracy)

B) The quantity of potable water supplied to the water distribution system including water imported and existing system sources, such as:

• surface water delivered via a water purification/treatment plant
• groundwater from wells delivered via a water purification/treatment plant
• purchased water (water imported)

C) The quantity of water metered or consumed and nonrevenue water lost within the distribution system

D) Operations and maintenance activities within the water distribution system, such as:

• continuous water system pressure readings
• maintenance activities related to water mains (e.g. number of water main breaks/repairs each year, blow-offs for water quality or freezing concerns, water main replacement or rehabilitation programs, water main flushing/swabbing/pigging programs, discharges at pressure relief valves, etc.)
• hydrant use or maintenance activities (e.g. physical inspection, fire flow testing, pool filling, temporary water services from hydrants, tanker truck filling, sewer cleaning, leaks on hydrants, etc.)
• valve maintenance activities (boundary valve between two different pressure zones, pressure-reducing valves within the water distribution system, maintenance on valve stems, seats, leaks on valves, check valve maintenance and inspection);
• water service and curb box inspection and maintenance (leaks on service connections)
• active leak detection programs
• reservoir use (filling/emptying throughout the day, cleaning, leakage, etc.)

ACTIVITIES TO REDUCE WATER LOSSES

Most water loss can be prevented by effective and proactive infrastructure management. The following infrastructure management activities will help reduce real water losses:

• Distribution system operation and maintenance to prevent breakdowns in equipment and the associated leakage (valves, hydrants, etc.)
• Material and construction standards to assure quality of future infrastructure installation
• Maintaining proper inventory to repair all sizes of main breaks or leaks
• Inspection of new water mains; observance of pressure and leakage tests
• GIS mapping of system components in order to quickly find valves to isolate main breaks
• Reporting leaks, repairs, complaints, theft, vandalism, etc, by geographic location to concentrate future leakage activities
• Increased surveillance in areas with aging infrastructure or reported leaks
• Periodically checking proper operation and control of pumps used to fill storage tanks
• Leak detection surveys/studies and leak repair
• Water main rehabilitation and replacement
• Pressure management

The following activities will help reduce apparent water losses:

• Metering of all source inputs, water exports or sales, and customer accounts (includes both billed, authorized use and non-billed authorized) 
• If not going to meter hydrant usage, accurately estimate and record the water used for firefighting or flushing
• Billing practices designed to detect potential problems or inconsistencies.
• Obtain consistent customer readings near the same day each month
• Eliminate or reduce human error by installing automated meter readers
• Account for non-billed authorized usage (such as hydrants)

Deterrence of theft or illegal usage by maintaining a visible presence, aggressively prosecuting those who are caught and soliciting public involvement in reporting such crimes. Accounting and record keeping practices to improve reliability and accuracy of the water balance more easily pinpoint areas with water losses.

MANAGEMENT STRATEGIES TO REDUCE WATER LOSS
There are numerous ways to reduce the loss of water. Deciding which program to use will depend on the condition of the local water infrastructure and the areas where water loss is occurring. Municipalities should consider one or all of the following programs to help in the reduction of water loss in their distribution system:

• metering
• leak detection and repair for both public and private water systems
• water efficiency/conservation (reduces apparent loss)
• valve maintenance
• pressure management including surge suppression
• infrastructure renewal
• conservation-oriented pricing (reduces apparent loss)
• speed and quality of repairs
• design standards for construction methods and pipe material
• nighttime flow analysis (reduces apparent loss)

A municipality applying these strategies and activities will benefit through reduced water loss and reduced costs to the utility. The importance of prioritizing active leak-control practices and procedures in the identification of water loss and the corresponding strategies to reduce leakage cannot be understated.

The municipality will not only increase revenues but also benefit through the extension of sustainable water supplies, reduced operating costs, improved system hydraulics and utility efficiency and improved environmental stewardship.

ADDITIONAL RESOURCES
Many additional resources on water loss control programs are available online or from the organizations and researchers listed below.

Thorton, Julian, 2002, Water Loss Control Manual. First edition. McGraw-Hill. New York, NY.
Waldron T. (2005) Managing and reducing losses from water distribution systems. Manual 10, Executive Summary. ISBN 0 7242 9498 8
AWWA, 1999, American Water Works Association Manual M36 , “Water Audits and Leak Detection,” The Manual of Water Supply Practices, AWWA, Denver.
AWWA, 2003, Applying Worldwide BMP’s in Water Loss Control , AWWA Water Loss Control Committee.