Water metering

Process of measuring water use

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A typical residential water meter

Water metering refers to the systematic approach of quantifying water consumption. The water meters are vital tools used to record the amount of water utilized by both residential and commercial properties that receive water through municipal supply systems. These devices also play a crucial role in assessing the flow rates within specific sections of the water network.

Globally, water consumption measurements are typically represented in units of cubic meters (m³) or liters; however, in the United States and select other nations, readings may appear as cubic feet (ft³) or US gallons on mechanical or electronic displays. Contemporary water meters often feature capabilities to indicate both the volume consumed as well as the real-time flow rate.

There exists a variety of water meter types, with distinctions made based on flow measurement techniques employed, target user categories, necessary flow rates, and required precision levels.

The landscape of water metering is evolving rapidly due to advancements in smart metering technologies and a wave of innovative solutions.

In North America, the manufacturing standards for water meters are primarily overseen by the American Water Works Association. Conversely, most other countries adhere to ISO standards for water meter functionality.

Diverse Water Metering Technologies

Flow measurement can generally be categorized into two main types: displacement and velocity techniques, each employing an array of distinct technologies. Notable devices in the displacement meter category include oscillating piston and nutating disc meters. On the other hand, velocity meters comprise designs such as single-jet, multi-jet, and turbine meters.

Additionally, there are non-mechanical models such as electromagnetic and ultrasonic meters, as well as specialty meters crafted for specific applications. Most standard water meters are tailored to process cold, potable water exclusively. In contrast, specialized hot water meters are constructed with materials engineered to withstand elevated temperatures. Reclaimed water meters, identifiable by their distinct lavender register covers, indicate that the water they measure is non-potable.

Moreover, we also encounter electromechanical meters, including prepaid and automatic meter reading (AMR) systems. The latter integrates an electronic measuring unit and an LCD display with a mechanical water meter, typically utilizing a reed switch or photoelectric coding register for signal output. The data from the electronic module's microcontroller can subsequently be transmitted to the LCD or integrated into a wider information management system.

Water meters are predominantly owned, monitored, and maintained by public utility providers, including municipalities, rural water associations, or private companies. Sometimes, operators of mobile home parks or apartment complexes may be billed based on one central meter reading, with costs distributed among residents using various criteria such as apartment size or occupancy levels, a practice known as submetering.

Understanding Displacement Water Meters

Displacement meters, often termed Positive Displacement (PD) meters, include common variants like oscillating piston and nutating disc designs. Their operation hinges on the water flow physically displacing a moving measurement element, which directly correlates the quantity of water flowing through the meter. The movement causes a magnet to drive the register.

PD meters traditionally deliver superior accuracy in low to moderate flow rates, ideal for typical residential and small commercial applications. They are generally available in sizes ranging from 5/8" to 2". However, their design makes them less suitable for large-scale commercial tasks that demand higher flow rates or lower pressure losses. PD meters typically include integrated strainers to shield measurement components from potential debris that may disrupt operation. The construction materials are often bronze, brass, or plastic, with internal components made from molded plastics and stainless steel.

Exploring Velocity Water Meters

Velocity water meters operate by gauging the flow rate within a meter of known capacity. The flow speed is then converted into a measurable volume, yielding insights into consumption patterns. Varieties of velocity meters include jet meters (both single and multi-jet), turbine meters, propeller meters, and magnetic meters. Most of these designs incorporate adjustments for calibration, ensuring accuracy in measurement.

Multi-Jet Meters

Multi-jet meters are particularly accurate within smaller sizes, typically ranging from 5/8 inches (16 mm) to 2 inches (51 mm) for residential and small commercial users. These meters leverage multiple ports around an internal chamber to produce numerous jets of water impacting a turbine; the turbine's rotation speed correlates to the water flow's velocity. While they excel at low flow rates, they lack the straight-through flow route necessary for larger-sized meters that accommodate high-flow scenarios. Built-in strainers serve to prevent clogging of jet ports. The outer casings are typically made of bronze alloy, while internal parts are often constructed using modern thermoplastics and stainless steel.

Turbine Meters

Turbine-based meters usually exhibit lower accuracy during modest flow rates compared to both displacement and jet meters. However, these devices maintain a design that does not block the full flow path, facilitating greater flow rates with less pressure loss than their displacement counterparts. They are commonly preferred for large commercial applications, fire protection systems, and as master meters in distribution scenarios. Protection strainers are generally advisable to be installed upstream to shield the measurement elements from sand or debris. Turbine meters are available in pipe sizes ranging from 1½ inches (38 mm) up to 12 inches (300 mm) or larger. The bodies are typically made from bronze, cast iron, or ductile iron, while internal turbine components may consist of plastic or non-corrosive metal alloys. Their accurate readings under regular conditions can be affected by flow profiles and varying fluid conditions.

• Fire meters are specialized turbine meters designed explicitly for high-flow requirements associated with fire protection. They are often certified by Underwriters Laboratories (UL) or Factory Mutual (FM).
• Fire hydrant meters represent portable turbine meters attached to hydrants to quantify the water flow. Generally made of lightweight aluminum, these meters are typically rated for 3 inches (76 mm). Utilities frequently require them for construction purposes, pool filling, or when permanent meters are yet to be fitted.

Compound Meters

Compound meters are essential where high flow rates are needed but low flow measurements must also be accurate at times. These meters utilize two measuring elements and include a check valve to manage the flow between them. At elevated flow rates, the water is directed primarily to the high flow meter, typically a turbine design. Conversely, when the flow diminishes to a rate where the high flow meter's accuracy wanes, the check valve redirects the water to a smaller element, typically a multi-jet or PD meter, which can effectively gauge lower rates. The cumulative values from both elements allow utilities to maintain a comprehensive record of total water consumption.

Electromagnetic Meters

Magnetic or "mag" meters are classified as velocity-type meters, utilizing electromagnetic principles to determine flow speed. This measurement hinges on Faraday's law of induction and necessitates either AC or DC power to operate the electromagnets. The absence of moving parts assigns mag meters an advantage in measuring bidirectional flow and lends itself well to applications in raw or wastewater, as there are no mechanical elements that may become obstructed or damaged. Strainers are unnecessary since no measurement components risk impairing flow through the system. Installation typically requires grounding measures to mitigate inaccuracies from stray electrical currents.

Ultrasonic Meters

Ultrasonic water meters utilize transducers to emit ultrasonic waves within the fluid to evaluate the water's velocity. Given the constant cross-sectional area of the meter, calculations of the water volume passing through can be executed with exemplary accuracy. To contend with the effects of temperature-induced density shifts, many ultrasonic meters measure water temperature as a key component in volume calculations.

Coriolis Water Meter

A Coriolis water meter serves as an advanced tool for accurately measuring fluid mass flow rates and densities, including water, employing the Coriolis effect. Unlike traditional mechanical meters built with moving parts, Coriolis meters utilize oscillating tubes through which the fluid flows. As fluid traverses the tubes, it triggers a phase shift in oscillation detected by sensors, correlating directly to mass flow rates. This metric also allows the determination of fluid density by analyzing the oscillating tube's natural frequency. Although it delivers high precision, the steep cost often limits inclusion in residential or municipal settings.

Water Meter Specifications: Length and Diameter

Standardized lengths and diameters of water meter tubes ensure compatibility with plumbing infrastructures and adherence to regulations. Diameters are generally measured by nominal pipe sizes (NPS), available from 15 mm (½ inch) to 300 mm (12 inches) or larger for industrial applications.

The ideal diameter is selected based on anticipated flow rates, with smaller sizes designated for residential use while larger versions target commercial or industrial applications. The installation length, commonly defined according to international protocols such as ISO standards, includes typical residential lengths of 110 mm, 165 mm, and 190 mm, influenced by regional practices. Larger industrial meters may exceed 300 mm in length, promoting interoperability and ease of integration into existing systems without necessitating alterations.

Displaying Water Meter Index

Reading Water Meter Registers

Water meters incorporate various registering systems. Standard registers generally feature a dial resembling a clock, showcasing increments that indicate the measuring units and consumed volume; if below the lowest digit displayed, they mimic odometer wheels. Modern registers rely on magnetic linking between a magnet within the measurement chamber and another positioned at the register's base to communicate consumption data. Gears within the register translate this movement into the correct usage increments shown on display wheels. Certain registers also come equipped with leak detection features—a small visible element geared closely to the drive magnet's rotation speed to highlight very minimal flows that typically go unnoticed.

Through Automatic Meter Reading technology, manufacturers have produced pulse or encoder registers that yield electronic data outputs for transmission to radio devices, loggers, or storage systems. Pulse meters relay digital electronic pulses to recording units. Encoder registers include electronic means allowing external inquiries to assess either the wheel positions or stored electronic values, frequently optimizing smart meter capabilities through regular data updates.

LCD Displays for Water Meters

Some water meters feature specialized registers equipped with LCDs as alternatives to mechanical wheels, or provide outputs for varied recording and control systems. Manuals often render the data in formats friendly for industrial purposes, delivering 4-20 mA analog outputs to record or regulate diverse flow rates and totalized figures.

Reading and Understanding Water Meter Values

Differing meter sizes signify various resolution readings. One sweep of the dial could correlate to 10 or 1,000 gallons (1 to 100 ft³, 0.1 to 10 m³). If one full sweep represents 10 gallons, and the sweep hand shows at 7 while the wheel display reads alongside a fixed zero, total usage would approximate to 1,234,567 gallons.

In the United States, billing commonly rounds to the nearest 100 or 1,000 gallons (10 to 100 ft³, 1 to 10 m³), often based solely on the leftmost digits displayed. Using the aforementioned example, customers would be billed 1,234 rounded to 1,234,000 gallons aligned to a 1,000-gallon billing resolution. Frequently, this rounding distinction is denoted through differing colored wheels; black digits may be ignored while white ones are considered for billing purposes.

Advancements in Smart Water Metering Technologies

Modern smart metering technologies for water meters signify an extensive evolution, enabling real-time monitoring and assessment of water consumption via connected digital devices. In contrast to conventional mechanical units, smart meters house electronic components that gauge water flow and relay this information wirelessly to both consumers and utility providers. Key technologies include Automated Meter Reading (AMR) devices, which facilitate one-way information exchange for consumption data, and Advanced Metering Infrastructure (AMI), allowing for two-way communication and features such as leak detection and adaptive billing. Smart meters often integrate with Internet of Things (IoT) systems that enhance water management efficiency, minimize waste, and improve user engagement.

Radio Frequency Technologies and Protocols

Radio Frequency (RF) technologies serve as a foundation for smart metering systems, allowing for wireless interactions between meters and utility networks. Various protocols and technologies pervade smart water metering applications, including:

• Wireless M-Bus (WMBus): Complying with the European EN standard, WMBus is prominent in Europe for utility metering across gas, electricity, and water domains. It provides secure and efficient communications tailored for utility requirements.
• Wize technology: Operating on the 169 MHz frequency, WIZE is engineered for long-range, low-power communication, widely applied for gas and water metering in Europe due to its outstanding penetration and scalability.
• LoRaWAN: Recognized for its long-range and low-energy capabilities, LoRaWAN suits deployments across rural and urban landscapes, finding application in various industrial and municipal operations.
• Zigbee: Favored in dense urban settings, Zigbee constructs mesh networks featuring energy-efficient and secure communication.

• NB-IoT and Cat-M: Serving cellular infrastructures, Narrowband IoT (NB-IoT) and LTE Cat-M technology facilitate direct connectivity with cellular networks, well-suited for mass deployments while delivering extended battery life and resilient coverage.
• Encoder receiver transmitter (ERT) technology is widely embraced for utility metering, notably within the U.S. This system connects meters via cables to Meter Interface Units (MIU), enabling smooth transitions between wired and wireless solutions, enhancing efficiency for service providers.

Protocol Layers in Smart Metering

Application-layer protocols transcend RF communication technologies to standardize data exchanges, reinforce interoperability, and bolster device functionality. These protocols facilitate seamless meter integration into expansive utility and IoT frameworks.

DLMS/COSEM (Device Language Message Specification/Companion Specification for Energy Metering) is celebrated as a predominant protocol choice for smart metering, offering a versatile and standardized data exchange framework among metering devices and utility entities. It accommodates diverse types of communication, ensuring secure data transmission and effective remote monitoring.

LwM2M (Lightweight Machine to Machine) was designed for IoT devices to provide efficient resource management and secure communications over restricted networks, ideal for smart meters and other low-energy devices that require remote configurations and real-time monitoring.

Additional protocols such as MQTT (Message Queuing Telemetry Transport) and CoAP (Constrained Application Protocol) are often employed within smart metering systems, especially among IoT-centered applications, focusing on high-efficiency communication in environments with limited bandwidth.

Overview of Smart Water Metering System Infrastructure

A smart water metering system comprises advanced meters, communication networks, and centralized platforms like Head-End Systems (HES) and Meter Data Management Systems (MDMS). Smart meters gather data regarding usage, pressure, and anomalies, transmitting it through wireless channels. The HES aggregates and verifies this information, subsequently relaying it to the MDMS for in-depth analytics, trend evaluation, and billing integration.

WMBUS Gateways for Remote Meter Reading

The WMBUS Gateway (Wireless M-Bus Gateway) serves as a communication medium for remotely reading water meters by connecting them with central data collection systems. This device typically operates on standard frequencies such as 868 MHz in Europe or other ISM bands.

WMBUS gateways can take the form of fixed installations designed to continuously gather data from nearby meters or part of mobile solutions like drive-by systems where handheld devices or equipped vehicles collect readings while passing meter locations.

In certain instances, electricity meters with integrated communication modules double as fixed gateways to amass data from proximate water and gas meters, optimizing deployment costs through leveraging existing infrastructures.

Data collected is sent to central servers using technologies like GSM, GPRS, LTE, or Ethernet for further analysis and management.

Key Applications and Advantages

The implementation of RF technologies and protocols facilitates the smooth distribution of smart water meters into utility frameworks, yielding numerous benefits:

• Enhanced Efficiency: Automated data collection minimizes manual effort and potential discrepancies.
• Proficient Leak Detection: Continuous monitoring helps swiftly identify and rectify leaks.
• Flexible Billing: Facilitates accurate and adaptable billing practices based on real-time consumption.
• Sustainability: Promotes water preservation through detailed consumption analytics.

Water Metering Prevalence

Water metering is widely practiced, especially in residential and commercial drinking water provision across numerous nations, along with industrial self-supply measures. However, it remains less common for irrigation agriculture, which consumes a vast portion of global water. Additionally, metering is infrequent in rural domains and small towns, though successful initiatives exist, notably in developing regions like El Salvador.

In most developed countries, utility-provided residential, commercial, and industrial metering is the norm, aside from the United Kingdom, where approximately 52% of users utilize meters. Conversely, metering levels vary in developing nations—for instance, Chile boasts a high rate of 96%, while Argentina remains relatively low.

Residential water metering rates across selected cities in developing countries are as follows:

• 99% in Santiago, Chile
• 96% in Abidjan, Ivory Coast
• 62% in Guatemalan cities
• 30% in Lima, Peru
• 28% in Kathmandu, Nepal
• 2% in Buenos Aires, Argentina

Almost two-thirds of OECD nations meter over 90% of single-family homes, while several countries, like France and Germany, progressively expand their metering efforts to include apartment buildings.

Advantages of Water Metering

The advantages of metering water are significant

• When combined with volumetric pricing models, it motivates users to conserve water.
• It assists in identifying and rectifying leaks within distribution systems, laying the foundation for reducing non-revenue water losses.
• Additionally, metering is essential for targeted assistance to low-income households requiring water subsidies.

Expenses Associated with Water Metering

The costs entailed in water metering comprise:

• Initial capital outlay for the procurement, installation, and potential replacement of water meters.
• Ongoing expenses associated with reading meters and preparing bills based on actual consumption, as opposed to fixed monthly fees.

While residential meter acquisition costs can be manageable, the total life cycle expenses of implementing metering systems may be substantial. For instance, retrofitting apartments in large buildings to install individual meters may necessitate significant and costly plumbing renovations.

Challenges with Water Metering

Metering challenges primarily arise in contexts where water supply is intermittent, an issue prevalent across many developing areas. Sudden pressure fluctuations could potentially damage meters, causing substantial inefficiencies as evidenced in various urban centers. Additionally, certain meters exhibit declining accuracy with time; under-reporting of consumption can lead to reduced revenue if defective units are not promptly replaced. A number of meters may also measure air flows, leading to inflated consumption readings, notably prevalent in systems with erratic supply; the resurgence of supply can inadvertently force air through the meters.

Displacement meters, lacking the ability to differentiate between air and water, may count both as fluid—an error that can lead to utility companies inaccurately billing for air. Regulations dictate that water metering systems must incorporate effective air or vapor elimination mechanisms to mitigate these occurrences.

Certification and Standards for Water Meters

Measurement Standards and Certification for Water Meters

Water meters must comply with specified measurement standards and certifications to ensure their accuracy and reliability. The leading standardizations include the ISO series and the OIML R49 guidelines, which clarify performance metrics, accuracy classifications, and water meter testing methodologies.

The European Union mandates compliance under the Measuring Instruments Directive (MID) for water meters distributed across member countries, ensuring conformity with established European standards.

In the United States, water meters typically align with the AWWA (American Water Works Association) C700 series standards, which define specifications concerning design, materials, and performance.

In Australia and New Zealand, the respective AS standard applies to water meters.

Certification procedures for water meters usually entail assessments of:

• Accuracy across varying flow situations.
• Integrity and durability against environmental stressors.
• Long-term stability assessments.

Potability Standards and Certification for Water Meters

Meters utilized in potable water frameworks are required to fulfill rigorous standards aimed at ensuring they do not compromise water quality or introduce contaminants. These criteria encompass materials, coatings, and designs that interact with drinking water.

In the U.S., adherence to NSF/ANSI 61 is mandatory, capping allowable leachable contaminants from water system components.

Within the EU, conformity to Regulation (EU) 305/ (Construction Products Regulation) is obligatory, supplemented by national certifications such as:

• United Kingdom: WRAS Approval.
• Germany: KTW Guideline.
• France: ACS Certification (Attestation de Conformité Sanitaire).
• Italy: DM 174/.

Australia and New Zealand also enforce an AS/NZS standard addressing products suitable for potable water engagement, focusing on various fundamental factors including taste, color, and toxicity.

In Latin America, countries like Brazil and Mexico frequently refer to international standards set by organizations like NSF International.

Addressing Environmental Constraints

Water meters are often installed in environments susceptible to rain, flooding, and dust, necessitating robust protective measures for sustained accuracy and operational reliability. Devices featuring an IP68 rating indicate both dust-tight construction and the capability to withstand continuous immersion past 1 meter depths, as prescribed by the manufacturer.

Manufacturers implement various mechanisms to achieve such environmental protection. Some include:

• Potting with Epoxy or Silicone Gel: Encapsulation of electronic components in durable substances like epoxy resin provides strong barriers against water ingress, where epoxy is recognized for its bonding strength and durability whereas silicone gel offers flexibility and thermal stability.

• Humidity Control with Sealants and Desiccants: Desiccants embedded within the meter housing maintain low moisture levels, helping prevent condensation that could yield corrosion or other electrical failures.

Innovations in Water Metering

Exploring Additional Sensor Technologies

Research into additional sensors integrated into water meters is underway, stemming from proof-of-concept (PoC) initiatives aimed at amplifying functionality and delivering enhanced insights into water usage and system performance.

These innovations are tackling challenges including leak detection, water quality oversight, and backflow awareness.

• Testing of pressure sensors seeks to identify discrepancies such as pipe bursts or blockages.
• Temperature sensors examine the potential for freezing conditions or variations in thermal profiles within water systems.
• Acoustic sensors are part of PoC testing for detecting leaks through analyses of sound patterns and vibrations within pipe systems.

Leveraging Data Analytics

Data harvested by smart meters is subjected to analyses that reveal water usage trends, peak consumption intervals, and possible inefficiencies or leakages within the system. This information empowers utilities to optimize water distribution effectively and address issues proactively.

Impact on Water Consumption

Discourse surrounds the influence of metering and pricing on water consumption patterns. The price elasticity of demand for metered water considerably varies according to local contexts. Generally, volumetric water pricing impacts consumption significantly when water expenses represent a substantial segment of household budgets.

Evidence from the UK indicates an immediate decline in consumption by approximately 10% upon meter installation; however, the lack of pre-installation consumption measurements leaves benefits unclear. Although metered households tend to consume less than non-metered equivalents, metering is not universally compulsory for homes built prior to specific cut-off dates, potentially creating a self-selecting user base. Certain stakeholders express concern regarding the socially regressive nature of water metering, as low-income households may struggle to afford water efficiency upgrades and consequently fall victim to "water poverty," defined as spending over 3% of net income on water and sewage services.

As evidenced in Hamburg, Germany, domestic water usage in metered units (112 liters/capita/day) registered a decrease of 18% when contrasted with unmetered residences (137 liters/capita/day).

Calibration and Verification of Water Meters

Water meter calibration and testing benches employ a variety of techniques to evaluate the accuracy and operational performance of water meters. These approaches are tailored to meet specific testing parameters, including flow variation, precision standards, or scalable capabilities.

Once flow rates are managed, several methodologies are applied to determine the accuracy and effectiveness of water meters. Key methods focus on comparing the meter readings against a validated reference standard.

• Start-Stop Method: A fundamental and commonly employed technique where flow initiation and cessation occur over a predetermined duration or volume, allowing the meter's reading to be compared against a precisely measured reference volume, thus ensuring reliable outcomes for low to medium flow rates.

• Gravimetric Method: Involving the collection of water over specific intervals, typically 60 seconds, and measuring its mass using highly precise scales.

• Volume Comparator Method: Employing a calibrated reference device, like a piston prover or master meter, to juxtapose the water volume registered by the test meter, recognized for its precision and suitability in compliance-focused applications.

• Real-Time Dynamic Measurement: Continuous flow systems leverage real-time data acquisition strategies to monitor the meter's readings against those reported by a calibrated sensor, optimizing efficiency for high-volume operations.

Understanding Prepaid vs. Postpaid Water Meters

Water meters are classified as either prepaid or postpaid, dictated by the payment frameworks employed. Predominantly, mechanical meters are postpaid, as are electromagnetic and ultrasonic variants. Prepaid systems necessitate users to purchase a specific water amount upfront from vending stations. The recorded water volume is then entered via mediums ranging from IC cards to RF devices for future consumption tracking. 

Prominent Water Meter Suppliers

• Sagemcom
• Kamstrup
• DH Metering Europe
• Honeywell / Elster (formerly Kent, Magnol, Wateau/Wameter)
• Farnier
• Hydrometer
• Itron (formerly Actaris, Schlumberger, Compagnie des Compteurs)
• Maddalena
• Smarteo Water (previously Polier Water)
• Sappel et Hydrometer (Diehl Group)
• Sensus (historically Sensus Metering Systems, Invensys, Socam)
• Tagus
• Zenner
• Arad

Related Topics

Cited References

Further Reading

• American Water Works Association Manual of Water Supply Practices Manual M6, Water Meters: Selection, Installation, Testing, and Maintenance, ISBN 1--017-2
• American Water Works Association standards C700-02: Cold-Water Meters; Displacement Type, Bronze Main Case
• American Water Works Association standards C701-02: Cold-Water Meters; Turbine Type
• American Water Works Association standards C702-01: Cold-Water Meters; Compound Type
• American Water Works Association standards C703-96: Cold-Water Meters; Fire Service Type
• American Water Works Association standards C707-05: Encoder-Type Remote-Registration Systems for Cold-Water Meters
• American Water Works Association standards C708-05: Cold-Water Meters Multijet Type

Explore more about Gravimetric & Piston Method Water Meter Test Bench for detailed information on water meters and their applications.