Water Loss Control - What Can Be Done?

Water utilities can control losses in their operations by compiling an annual water audit of their supply operations, and by implementing programs to identify and contain inefficiencies.  Such programs include leakage management, meter 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.  Losses also occur as real losses or 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.Controlling Apparent Losses

Three sub-categories of apparent losses have been defined as given below: 

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 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, thereby a measureable loss is incurred.  Water utilities should closely monitor customer consumption trends to identify meters that have lost accuracy.  Meter testing should be conducted on an ongoing basis to stay on top of the disposition of the meter population.

Systematic Data Handling Errors

This includes errors 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 under-statement of actual consumption volumes.  Such errors distort assessments of customer consumption (such as for water conservation purposes) 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 allows 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 lost 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.

Unauthorized Consumption 

Unauthorized consumption can occur in many manners as there are always unscrupulous persons who contrive 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 must generate revenue for water utilities to meet their cost of service.  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 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 effectively 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.  The current approaches include four prongs of attack:

Active Leakage Control

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. 

Speedy, quality repairs – once a leak of 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.

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. 

Pressure Management

Intuitively it is easily understood that 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 joints.  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.

An array of new equipment and technologies now exist to give water utilities 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.

Getting Started

Compiling a water audit – even one based on preliminary data – is the best way to get started.  Along with quantifying volumes of apparent and real losses, make sure that you assess the cost impact that these losses are exerting on the water utility operations.  Once the cost impact of the losses are known, justifications can be made to launch the efforts that will recoup these costs.

Water Loss Control References

A number of recent research reports and publications are available that explain the best practice approaches to water loss control:

Research Report for Project 2811:  Evaluating Water Loss and Planning Loss Reduction Strategies, Water Research Foundation (formerly the American Water Works Association Research Foundation), 2007  This work assessed water audit methodologies in use and concluded that the method ultimately adopted by AWWA and IWA is the most robust.  Guidance is also provided on the assessments and strategies to employ to launch an effective water loss control program.  Click here to go to the AWWA bookstore.

Research Report for Project 2928  Leakage Management Technologies, Water Research Foundation, 2007  This project piloted successful international leakage management interventions in several North American water utilities.  Techniques such as the use of district metered areas and pressure management were demonstrated.  The conclusions found that, with the use of site-specific design elements, these techniques have applicability in North American water utilities and offer new means to control leakage effectively.  Click here to go to the AWWA bookstore.

Water Loss Control, 2nd Edition, 2008  This comprehensive text provides information on the AWWA/IWA Water Audit Methodology and state-of-the-art methods to control both apparent and real losses.  It offers a large array of case study accounts that detail how water utilities from around the world are achieving dramatic reductions in water and revenue loss.  Click here to go to the AWE on-line publication order form. 

More Information

AWE Water Loss Control Introduction 

Water Audit Process Introduction 

Case Studies - The Emerging Use of Water Audits in the US