Water Loss Control Programs

Water loss control includes utility efforts to manage leakage to economically low levels, and reducing metering and billing errors such that reliable measures of customer consumption are attained and sufficient revenue is garnered by the water utility. Utilities should adopt policies for non-revenue water and water loss control just as they adopt policies for purchasing, procurement, personnel, and other utility program areas. A template non-revenue water policy that can be adopted by a municipality or water loss utility is available. 

After compiling an annual water audit, water utilities can control losses in their operations by implementing programs to identify and contain inefficiencies. Such programs include leakage management, meter accuracy testing and enforcement against unauthorized consumption of water.

Losses in water utility operations occur in two distinctly different manners. “Apparent” losses occur due to customer meter inaccuracies, billing system data errors and unauthorized consumption. These losses cost utilities revenue and distort data on customer consumption patterns. “Real” losses are water that escapes the water 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.

Specific interventions exist to combat both apparent and real losses. It is important that the water utility determine the cost impact to the water utility from its apparent and real losses, and design an intervention strategy that takes into account the water resources and economic benefits of containing these losses.

Apparent Losses: Customer Meter Inaccuracy. The majority of North American water utilities provide their customers with water meters to measure consumption.  Most meters retain accuracy over long periods of continuous use, but many types of meters can lose accuracy quickly once they reach a threshold level of high cumulative consumption. This level varies among the various meter models. Inaccurate meters tend to under-register consumption volumes, resulting in a loss in revenue to the utility. Thus it is important that utilities closely monitor customer consumption trends to identify meters that have lost accuracy.  Meter accuracy testing should be conducted on an ongoing basis, and usually a sample of the meter population is tested regularly.

Apparent Losses: Systematic Data Handling Errors. These errors occur in the meter reading, billing and data archival paths of the water utility. A water utility may have accurate customer meters, but unless the integrity of the consumption measure is ensured throughout the entire path, then errors can appear on customer bills or management reports. Often such errors lead to an understatement of actual consumption volumes. Such errors distort assessments of customer consumption (compromising water conservation assessments) and cost utilities revenue. Water utilities should assess these practices to determine if inefficiencies exist such as poor meter reading results from access limitations to meters or human error in transposing meter readings manually. Billing policies and procedures should also be reviewed. Do policies allow some customers to go unmetered or unbilled? Do all customers exist with an account in the customer billing system (whether or not the system is metered)? Flowcharting the billing system process is a relatively quick way to uncover possible gaps in procedure or policy that allow groups of customers to go unmetered or unbilled. Often municipally-owned buildings are unmetered and unbilled, usually on the basis that they do not generate revenue for municipally-owned water utilities.  However, left unmonitored, these buildings often waste water due to plumbing leaks or wasteful practices and the loss water goes undetected. Water utilities can often find significant uncaptured revenue that can be recouped once an evaluation of the billing information handling process is undertaken.

Apparent Losses: Unauthorized Consumption. Unauthorized Consumption can occur in various ways, including theft and contrived ways to avoid paying for service. Water utilities should have clearly defined policies and regulations for water service provision, and means to detect common breaches in the supply, metering and billing processes. Utilities should likewise have policies for customers who encounter a true inability to pay for water service. Unauthorized consumption results in wasted water resources and billings lost by the water utility. This often results in additional cost being passed along to the paying customer population.

Drinking water is a critical service for communities but this service must generate revenue for water utilities to meet their cost of service in maintaining the water infrastructure. Adequate revenue capture relies upon efficient systems of customer metering, meter reading, billing and enforcement that prevent consumption data error – and revenue loss – from occurring. For most water utilities the customer billing system also becomes the de facto customer consumption database, and many functions rely upon the integrity of the customer consumption data that is included here. When consumption data integrity is corrupted by such errors, the effects of water conservation programs might not be accurately assessed. Similarly, demand data for water distribution system hydraulic modeling or planning studies may be corrupted. Water utilities have many persuasive reasons to assess and contain apparent losses in their operations.

Controlling Real Losses. Many drinking water utilities around the world respond to leaks only after they have received a report of water erupting from a street, a complaint from a customer about a damp basement, or other visible signs of leakage. Utilities that employ this type of reactive leakage response most likely have excessive leakage that will never be comprehensively contained. Controlling leakage effectively relies upon a proactive leakage management program that includes a means to identify hidden leaks, optimize repair functions, and upgrade piping infrastructure as its useful life ends. The science of leakage management has evolved rapidly, and is moving from a singular “find and fix” approach to a more comprehensive “predict and prevent” strategy.

Real Losses: Active Leakage Control. This includes seeking hidden, or unreported leaks by sonically canvassing the water distribution system (leak detection survey) or using automated leak noise monitoring or minimum hour flow analysis to detect newly emerging leaks as they occur.

Real Losses: Speedy, Quality Repairs. Once a leak or rupture is known, water utilities must be able to respond quickly to effect quality, lasting repairs. Repair policies also play a role here, typically regarding leaks on customer service connection piping. Many water utilities require that their customers arrange for repairs on their leaking service piping. This policy often results in delays in getting known leaks repaired. Alternative approaches such a warranty or insurance programs for customer service lines can be more effective in ensuring timely leak repairs.

Real Losses: Pressure Management. Water escapes faster from a leak at a relatively high pressure than water leaking at relatively low pressure. Yet most water utilities do not take into consideration the effects of excessive pressure levels that may exist in parts of their water distribution systems. Pressure management is one of the more recent, and highly effective, means to control excessive leakage losses. It is particularly effective for systems that suffer high levels of background leakage, which is the collective leakage from many weeps and seeps at pipe joints and fittings. Reducing pressures at low demand hours has been found to be very cost-effective in reducing background leakage. Pressures into discrete pressure zones or District Metered Areas (DMA) can be controlled by pressure reducing valves (PRV) that regulate water supply pressure into the zone.

Real Losses: Water Main Rehabilitation and Replacement. All pipeline assets eventually reach the end of their service life and must be rehabilitated or replaced. Water utilities should have in place funding and programs to identify expiring assets and ensure that they are reconditioned to continue to provide reliable service.

Real Losses: Leakage Component Analysis. By using data collected by a water utility on the number and types of leaks found and repaired in their water distribution system, a Leakage Component Analysis can be conducted to help utilities determine the extent of leakage control activities that are economic to undertake. This method segregates water system failure events into Reported leaks and breaks (visible leakage), Unreported leaks (hidden leaks), and Background Leakage (hidden weeps and seeps that are acoustically undetectable but responsive to pressure management).

There are three time periods in the life of a leak which must be are approximated. These are the Awareness period (leak emergence until the utility becomes aware of the leak), the Location period (time needed to pinpoint the leak source), and the Repair period (time to halt the flow of water leakage). A primary goal of the leakage control strategy is to limit the duration in which leaks run, since annual leakage losses are aggravated by long leakage durations more than the magnitude of the leaks. By setting an objective to contain the Awareness, Location, and Repair times, water losses from a leak can be minimized.

Every each water utility encounters a unique production cost for their water supply, and unique labor and equipment costs for leakage control. The component analysis takes these system-specific costs into account when determining the range of leakage control activities that are most suited economically for the utility to undertake.

Fortunately a free tool exists for water utilities to employ to conduct a leakage component analysis. The Water Research Foundation and the United States Environmental Protection Agency sponsored the research project Real Loss Component Analysis: a Tool for Economic Water Loss Control. The project produced a spreadsheet software tool that provides users with an easy format to enter data on the leakage events that occur in a water utility over the course of a year. Utilizing various data from the standard water audit, the tool calculates the economically optimum leakage levels and relates the appropriate leakage control activities such as acoustic leak detection and pressure management to reduce leakage in the water distribution system.

An array of effective leakage control equipment and technologies exist to provide water utilities with the tools to combat leakage and manage real losses to economically low levels. However, it is incumbent upon each water utility to be proactive in implementing a leakage management program. Merely responding to reported leaks and breaks when they surface means that the water utility is not in control of its leakage, which will inevitably continue to rise over time.

Tools and Guidance for Small and Rural Water Utilities. The Water Research Foundation sponsored a project entitled Pipe Location and Leakage Management for Small Water Utilities that created technical guidance modules to assist small systems operators in locating their buried infrastructure, identifying water loss sources, and locating leaks.