Choosing the Right Residential Water Metering Technology

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1 WHITE PAPER Choosing the Right Residential Water Metering Technology ABOUT THE AUTHORS Dr. Mark England is CEO of Sentec Ltd., a research and development organization within Sensus, a Xylem brand, that develops sensor technologies for utility and infrastructure applications. Mark holds a Physics degree and Ph.D from the University of Cambridge, UK, and has over 20 years experience designing metrology solutions for measuring water, gas and electricity. He currently resides in Cambridge, UK. Dan Pinney is the Senior Director of Global Water Marketing at Sensus, a Xylem brand. Dan has more than 25 years of experience in the global water industry with leadership roles in operations, development and marketing. Dan holds an electrical engineering degree from the University of Florida. He currently resides in North Carolina, USA. RISING DEMANDS ON METERING DECISIONS Accurate and dependable water metering is more important than ever for today s water utilities. Although utility managers are tasked with meeting tight budgets, it is imperative for utilities to invest in their water metering infrastructure because: Water meters are considered to be the utility s cash registers, so ensuring accurate measurement of all water usage is essential for obtaining sufficient revenue. Regulatory compliance pressures also contribute to these decisions as regulatory agencies strive for the metering of all water, within specific accuracy limits. Customer service expectations are growing. Utility customers demand excellent service in the form of accurate bills and helpful communication from the utility, such as leak notifications. They also want to understand their usage patterns and how their bill is affected. Water conservation is also crucial for most utilities today, as water scarcity continues to impact more communities. Proper measurement and leak detection are key to reducing water waste and ensuring sustainability.

2 When making meter selection decisions, utilities must consider several factors. These include service size, application, and expected flow rates. There is no one type fits all application when it comes to meter technologies. To ensure the right meter is used in the right place, utilities have to upgrade meter programs with more specific profiles. TECHNOLOGY CHOICES FOR RESIDENTIAL METERING Utilities have a variety of technology choices for residential metering. However, choosing the right meter may result in increased revenue, improved customer service, conservation of critical water resources, and environmental sustainability. Residential metering technology falls into two broad categories mechanical meters and static meters. Within those categories are various sub categories or types of meters. MECHANICAL METERS Mechanical meters use either positive displacement or velocity to measure usage. In a positive displacement (PD) meter, water physically moves an oscillating piston or nutating disc as it flows through the meter. PD meters calculate the volume of water consumed by counting the number of reciprocations or revolutions of the piston or disc. Jet and turbine meters measure the flow velocity based on an impeller s rate of rotation as water flows through the meter. The velocity is then used to infer the volume of water used. Overall, mechanical meters are very dependable at a variety of flow levels. They are relatively low in cost. However, these meters are prone to the following issues: Mechanical parts are susceptible to effects of sediments and debris, corrosion, tuberculation, scale formation and water chemistry. Moving parts in the meters wear out over time. To maintain performance, mechanical meters require periodically sampled inspection processes, commonly known as meter testing programs. Meters with worn parts result in underregistration and loss of revenue with age, particularly at lower flow rates. As a result, all mechanical meters should be replaced after a specified period, unless meter testing shows they are still operating to specification. Some mechanical meters (those with better tolerance of poor water quality) have poor low-flow accuracy, even when new. Mechanical meters meet AWWA guidelines and are acceptable for standard billing purposes. However, more accurate metering technology brings in muchneeded revenue to fund system operation and maintenance. Also, utilities are under pressure to conserve water, especially in drought prone areas. Improved metering accuracy helps to preserve the resource. There s a better way to measure residential water use.

3 STATIC METERS Static meters are solid-state meters with no moving parts to wear out, degrade or break. As a result, static meters can maintain the same level of accuracy long-term, especially at very low flows. Static meters also reduce maintenance requirements. They do not need meter testing programs. Nor do they have as high a frequency for repair and replacement as mechanical meters. While the initial cost of a static meter may be higher, the meter s long-life accuracy, low-flow measurement capability, and reduced maintenance result in a lower life cycle cost than a mechanical meter. TYPES OF STATIC METERS Types of residential static meters include fluidic oscillator, ultrasonic, and electromagnetic technologies. FLUIDIC OSCILLATOR TECHNOLOGY Fluidic oscillator meters were firstgeneration static meters. They work by exploiting fluid dynamics to switch flow between two internal channels. Oscillation frequency increases with flow, like a flag fluttering in the wind. These meters have limited performance at low flow rates, as they stop oscillating when the flow is too low. To make the meter oscillate at lower flows, a tighter restriction would be required, leading to excessive head loss. The meters also have relatively large head losses at medium and high flows, which can cause poor high-flow performance for the customer. ULTRASONIC TECHNOLOGY Ultrasonic meters measure the instantaneous speed of the water. They do this by measuring the difference in transit time of sound pulses with and against the direction of flow. The volumetric flow rate is determined by complex internal linearization and correction calculations within the meter. Ultrasonic meters produce very accurate measurements on the test bench. However, certain field conditions may affect their performance. These include turbulence created by upstream valves or elbows, temperature, and viscosity. Particulates and bubbles may also be problematic. They tend to scatter and reflect ultrasonic pulses. The typical effect is the meter s electronics get a grossly invalid dataset and stop measuring. The result is under-registration and unaccounted-for water. For poorer quality water, this problem negates the register accuracy advantage of static meters. While ultrasonic technology is very effective for measurement of larger pipe diameters, problems exist with small diameter pipes. In most cases, mirrors and supports must be installed in line with the flow to reflect acoustic signals. Reflectors and supports within the pipe create convoluted flow paths within the meter, and disturbances in these flow paths may affect accuracy.

4 Also concerning is the potential for degradation or damage to the reflectors. These sensitive and critical components are constantly exposed to the flow and any sediment in the water. ELECTROMAGNETIC TECHNOLOGY Electromagnetic meters measure flow based on the voltage generated when water passes through a magnetic field in a section of insulating pipe. This voltage is proportional to the flow rate over a much wider range than any other flow metering technology. Magnetic metering technology is a longestablished method of flow measurement for larger diameter pipes. When adapted to residential meters, it has several advantages over other static meter technologies. The Sensus iperl water meter The technology is fundamentally immune to real-world field disturbances. Temperature variation, vibration, particulates, air bubbles, and flow disturbances have no effect on the meter s accuracy. Electromagnetic meters have no impediments within the pipe to disturb the flow pattern. Also, no sensitive reflectors or other components are exposed to effects from the water. In a well-designed residential electromagnetic meter such as the Sensus iperl meter, the flow measurement is inherently linear by design. Electronics remain in calibration by design as well. Unlike ultrasonic meters, an electromagnetic meter provides continuous measurement, rather than a series of snapshots. This means that real-world intermittent consumption of water is accurately captured. ELECTROMAGNETIC: THE BEST RESIDENTIAL METERING TECHNOLOGY Utilities need meters that have a high degree of accuracy. They also need meters with a certain degree of ruggedness, dependability, and long life in the field. Simplicity of operation and installation is important, too. As noted above, electromagnetic metering technology has several advantages over other meter types. Through careful design, electromagnetic meters can be extremely accurate at low-flow rates and can achieve long-term accuracy. Utilities that use electromagnetic water meters can expect the following benefits: Long-term accuracy Ability to measure with great accuracy at very low flow

5 Choosing electromagnetic metering technology combined with smart metering features is the right decision for residential applications. Better high-flow durability No restrictions on installation orientation No effects from flow disturbances Not affected by field disturbances vibration, temperature, particulates, air bubbles Linear flow measurement by design no complex internal linearization Continuous measurement for great accuracy with intermittent flow Reliable detection of empty pipe and backflow conditions. No components within the pipe to disturb the flow pattern or be exposed to damage ADDITIONAL SMART METER FEATURES In the introduction, it was noted that meters are considered the utility s cash registers. However, today s meters have advanced capabilities. In addition to the applied measurement technology, utilities should consider the potential smart features available for residential use. Smart meters can send detailed data directly to the utility through radio communication. Access to this data allows customer service staff to quickly answer questions about water usage and billing from the office. Online portals allow customers to view their accounts from a computer or smartphone. This saves time for the operations staff while improving customer satisfaction. These meters are also designed to discourage tampering, a common source of non-revenue water. Smart meters can detect and provide notification for field conditions such as customer leaks, reverse flow, and high or low pressure. These alarms can prevent property damage or dangerous backflow conditions. Further advancements in smart meter functionality allow the utility to regulate water use remotely. Remote shutoff features relieve the burden on utility staff at the office and in the field. Benefits for customers include faster shut-offs for leaks and scheduled turn-ons as requested. CHOOSE THE RIGHT RESIDENTIAL WATER METERING TECHNOLOGY By choosing the right metering technology, utilities can reduce non-revenue water, improve customer service, and better sustain the resource. Water metering technologies have evolved from basic water usage measurement to become important water management tools. A variety of metering technologies are available, and utilities must determine which meter works best for certain applications. For residential metering, accuracy at low and intermittent flow is essential. Meters must also be able to measure accurately despite the imperfect conditions in the field.

6 RESIDENTIAL METER TECHNOLOGIES COMPARISON PD Meter Fluidic Oscillator Ultrasonic Electromagnetic Inherently linear response No moving parts Flexible orientation Accurate at low flow Tolerates dirt and debris Accurate long-term Low pressure loss Immune to disturbed flow Stable over temperature Immune to vibration Measures intermittent flows Performance: low medium best Choosing electromagnetic metering technology combined with smart metering features is the right decision for residential applications. ABOUT SENSUS IPERL AND ALLY METERS Much innovation has gone into the design of Sensus iperl and ally water meters. These meters have patented electromagnetic technology from Sensus, and are designed to put physics to work. Sensus iperl meters boast inherently linear Cutaway view of the Sensus ally water meter featuring the 3-state ball valve performance and stable electronics. They measure residential flow profiles with great accuracy and are designed to capture revenue from real-world usage patterns and flow levels over a 20-year battery life. Sensus ally meters have the additional feature of an internal 3-state ball valve allowing for remote service turn-on, shutoff or restricted use. A proprietary actuator operates the valve. Because the valve is located within the meter, no external piping modifications are needed to gain the benefits of remote operation. Additionally, pressure and temperature sensors are included to provide all smart meter capabilities. Both the Sensus ally and iperl meter are smart meters that provide higher accuracy, more flexible installation configuration, and a long battery life. Through a combination of the right measurement approach and smart features, these meters are integral to successful revenue capture, recovery and protection within residential applications.

7 BENEFITS OF SENSUS ELECTROMAGNETIC METERS Meter accuracy, including low flows down to 0.03 gpm. Installation orientation flexibility. Lower maintenance in terms of testing and replacement. Immune to effects of temperature, particulates, air bubbles and vibration. Reliably detects empty pipe conditions. Smart Water alarms high flow, reverse flow, empty pipe, leak & tamper. Remote turn-on, shut-off or restricted use and high/ low pressure and temperature sensing with Sensus ally meters. ABOUT SENSUS Sensus, a Xylem brand, helps public service providers from utilities to cities to industrial complexes and campuses do more with their infrastructure to improve quality of life in their communities. We enable our customers to reach farther by responding to evolving business needs with innovation in sensing and communications technologies, data analytics and services. WPW Sensus 8601 Six Forks Rd, Ste 700, Raleigh, NC sensus.com