Each day billions of gallons of treated drinking water are lost from the leaking distribution systems of public water suppliers. The U.S. Environmental Protection Agency (EPA) estimates that water losses are responsible for more than $2.8 billion in lost revenue each year for water suppliers across the nation. In an effort to shed light on these water losses that water engineers, maintenance professionals and pump operators often experience firsthand, the Natural Resources Defense Council (NRDC) launched "Cutting Our Losses: State Policies to Track and Reduce Leakage from Public Water Systems," an interactive website that highlights how states and utilities are adopting water loss accounting to more accurately assess this nationwide problem.
States and utilities face the following challenges that perpetuate the loss of billions of gallons of water and associated revenue every year because of leaky pipes:
- Aging and failing infrastructure: The condition of our nation's drinking and wastewater infrastructure has been given a failing grade of "D" by the American Society of Civil Engineers. To continue to provide safe drinking water, EPA estimates that community water systems will need approximately $384.2 billion during the next 20 years. EPA includes expanding, replacing or rehabilitating existing infrastructure, as well as constructing new infrastructure in that estimate.
- Climate change: Extreme weather events, sea-level rise, temperature changes, and shifting precipitation and runoff patterns challenge the abilities of states and utilities to protect water quality and quantity. These changes can impact a utility's ability to access reliable water supplies, provide effective flood management and maintain affordable rates. These changes also can impact a utility's customer base, causing fluctuations in demand and patterns of use.
Accounting for and controlling water loss helps utilities address these dual challenges, first by helping them to better manage their existing infrastructure and control costs. Water loss programs can help utilities identify water losses that are economically recoverable and that are cost-effective to identify and eliminate. One study quoted by EPA estimates that up to 75 percent of losses are cost-effectively recoverable.
In addition to infrastructure investment, utilities face other costs associated with leaky and aging pipes. Water main breaks typically come with costly emergency repairs, street closings, traffic disruptions, loss of water pressure, curtailment of service and boil-water advisories. Conversely, water loss reduction increases system resiliency, reduces weather-related risks, protects water resources and shields residents from excessive utility rate increases.
The American Water Works Association (AWWA) developed a standardized method to conduct water audits and help water utilities track their distribution system losses. Once a water system accurately identifies losses, it can implement strategic controls to reduce them.
A Pivotal Role for Pressure Management
As any drinking water professional knows, maintaining adequate pressure in the distribution system is essential for public safety (fire protection), public health (backflow prevention) and customer satisfaction. Even though sufficient water pressure is essential for good system operation, more is not always better.
Excessive pressure can contribute to water hammer, with the potential for damaged plumbing and customer annoyance.
Pressure directly affects the running rate of all leakage, so unnecessarily high pressure produces an extra increment of water loss. Elevated pressures also raise the floor from which pressure transients arise. These microbursts of pressure, often at multiples of average system pressure for fractions of a second, are thought to exacerbate the more gradual effects of age, corrosion and vibration that attack the integrity of buried piping.
New work now links water distribution system pressure to the frequency of water main breaks. The upcoming Fourth Edition of AWWA's Manual M-36, "Water Audits and Loss Control Programs," due to be released in December 2015, will have an expanded discussion of pressure management, including more specific guidance for determining average system pressure.
The new manual will also include formulas for relating changes in system pressure to changes in main break frequency. Tamping down unnecessary and excess pressure is likely to emerge as a leading tool for saving water and for cost-effectively extending the life of distribution system piping.
The implications of this development for operators are substantial. Water main breaks are the most visible and objectionable manifestations of water infrastructure failure. In cities like Los Angeles where water pressure in more than half of the city's 113 pressure zones is unnecessarily high, water managers and their governing boards will want to learn more about where pressures are excessive and how they can be reduced.
Specific steps will vary from system to system. Pressure reduction can start with relatively simple adjustments to tank levels, pump controls and existing pressure reducing valves (PRVs). More advanced interventions would involve the placement of additional PRVs in the system and evaluation of flow-modulated pressure control valves.
Hydraulic modeling might also suggest the division or recombination of certain pressure zones to remove pockets of excess pressure. New attention to transients can also be expected, including deployment of transient monitoring sensors and revised operating procedures to better ensure that valve openings and closings and pump operations are properly attenuated to reduce the frequency and severity of pressure transients.
State Action Is Essential
Unfortunately, without direction from state regulators or auditors, many public water utilities are reluctant to aggressively self-audit and have not implemented water audit best practices described by AWWA. Fortunately, the tools already exist to address water loss. By embracing them, states can help achieve real monetary savings for public water utilities and their customers and taxpayers. To know when and where to deploy these solutions, annual, standardized water loss auditing should be undertaken by all public water suppliers.
Water Loss Accounting: The BasicsWater loss accounting is a cost-effective, systematic approach that helps utilities detect, locate and correct leaks. It is strongly endorsed by the American Water Works Association (AWWA) and presented in AWWA's Manual M-36, "Water Audits and Loss Control Programs." The manual offers standard methods and terminology to perform water audits and to assist water utilities in tracking their distribution system losses. AWWA also provides free audit software available for any utility to download. Water loss accounting helps utilities identify two types of loss from their systems: real (physical) losses, which include costs to a utility from the additional energy and chemical usage required to treat lost water, and apparent losses (water that is used but not billed). These are the primary components of non-revenue water—water the utility spends capital and operating dollars to obtain, treat and transport, but which generates no revenue. These costs, along with the costs of repairing the damage caused by water main breaks and leaks, are simply passed along to rate payers in the form of higher water charges. Until a utility identifies and categorizes its losses, it cannot effectively implement the distinct strategies necessary to reduce them cost-effectively.
Cutting our Losses"Cutting Our Losses: State Policies to Track and Reduce Leakage from Public Water Systems" is an interactive website that highlights how states and utilities are addressing distribution system water loss through water loss auditing. NRDC's website tracks the policies leading states have adopted to standardize the reporting of water losses and set goals for its reduction. The site answers the following questions:
- How is your state doing compared to other states? What is your state's grade for the strength of its water loss reporting policies? Does it require more than rudimentary water loss reporting? If so, does your state set targets for water loss reduction?
- What states are leading the way on water loss accounting? What can other states learn from them?
- What does a validated water loss audit look like?
- What key questions are consumers asking about how their utility is addressing water loss?
- What are upcoming training opportunities?
- Where can you get the latest research on water loss?