Classe B contatore dell'acqua remains one of the most widely used mechanical water meter types for residential and light commercial water metering due to its balanced combination of accuracy, cost-effectiveness, and long-term operational reliability.
What is a Class B Water Meter?
A Class B water meter is an older accuracy class used in older international standards (such as ISO 4064:1993). Under these older standards, water meters were classified into four accuracy classes—A, B, C, and D—based on their measurement performance, with performance typically increasing from Class A to Class D.
- Class A:Lowest performance, narrowest measurement range.
- Class B:Balances performance, sensitivity, and cost.
- Class C / D:High-performance classes, typically used in applications with strict requirements for low-flow measurement.
As Class B water meters can meet the metering needs of most residential and general commercial settings, they have long been the mainstream type for residential and light commercial applications. Precisely because of their widespread use, even though international standards have been updated, many manufacturers, distributors, and end users still habitually use “Class B” to describe water meters suitable for routine metering scenarios with moderate performance.
The current international standard ISO 4064-1:2014 no longer uses the A/B/C/D classification system for measurement classes, but instead uniformly adopts the classification method of “Accuracy Class 1” and “Accuracy Class 2.” The “Class B water meter” in older standards is generally considered to be broadly comparable to “Accuracy Class 2” in ISO 4064:2014, although the two systems are not directly equivalent. Additionally, the industry is gradually shifting toward using the R-value (range ratio) to measure water meter performance, such as R80, R100, and R160. In general market practice, Class B meters are often associated with R80-level performance, while Class C is commonly associated with R160, depending on the design and metering mechanism.
Advantages of Class B Water Meters
Compared to Class A accuracy, Class B offers higher measurement sensitivity and lower measurement error, providing more precise water volume measurement under various flow conditions and ensuring billing fairness.
Compared to Class C and Class D accuracy classes, Class B is more cost-effective. In the actual market, if the material, structure, and other parameters of the same water meter model are identical, and only the accuracy class is upgraded from Class B to Class C, the price difference is typically only about 5%.
From a procurement and operations perspective, as the mainstream product in the market, Class B water meters offer convenient spare part replacement and abundant supplier resources. They also comply with multiple international standards such as ISO 4064, OIML R49, and GB/T 778, resulting in low long-term maintenance costs, making them the preferred solution for standard metering needs.
Class B Water Meter Product Recommendation
As one of China’s leading water meter manufacturers, Misuratore BMAG has over 20 years of experience in water meter R&D and export, with products sold in more than 80 countries and regions worldwide. We offer a variety of Class B water meter solutions compliant with international standards such as ISO 4064 and OIML R49.
For different application scenarios, BMAG provides a wide range of Class B product models, including single-jet, multi-jet, cold water meters, and hot water meters:
Class B Water Meter Common Technical Specifications & Performance Parameters
To accurately assess whether a Class B water meter is suitable for specific residential or commercial applications, it is essential to understand the relevant technical specifications and performance parameters prior to procurement. These parameters not only define the meter’s measurement capabilities and operational limits but also directly influence its long-term measurement accuracy, durability, and the overall operational efficiency of the system.
1. Operating Flow Range & Ratio
The flow range parameters indicate the range of flow rates within which the water meter can maintain the specified measurement accuracy. According to ISO 4064, the operating flow range of a water meter is typically defined by four key parameters: Q1, Q2, Q3, and Q4. In addition to the basic flow parameters, modern water meter specifications also place significant emphasis on the R-value (range ratio or turndown ratio), which indicates the meter’s low-flow measurement capability and overall measurement range.
Learn About the Details of Water Meter Flow Rates & Ratio Here: https://www.bmagmeter.com/understanding-water-meter-flow-rates-q1-q2-q3-q4-and-r-ratio/
The table below shows the typical operating flow range parameters for Class B water meters:
| Misurare | Unit | Dn15 | Dn20 | Dn25 | Dn32 | Dn40 | Dn50 |
| R | Q3/Q1 | 80 | |||||
| Q4 | m³/h | 3,125 | 5,000 | 7,875 | 12,500 | 20,000 | 31,250 |
| Q3 | m³/h | 2,500 | 4,000 | 6,300 | 10,000 | 16,000 | 25,000 |
| Q2 | L/h | 50 | 80 | 126 | 200 | 320 | 500 |
| Q1 | L/h | 31.25 | 50 | 78.75 | 125 | 200 | 312.5 |
2. Accuracy Bands
The Maximum Permissible Error (MPE) is the key criterion for assessing the measurement accuracy of water meters. ISO 4064 divides the operating flow range of water meters into a Lower Zone and an Upper Zone, and specifies different error limits for each zone.
Learn More Knowledge About Water Meter Accuracy Class Here: https://www.bmagmeter.com/comprehensive-understanding-water-meter-accuracy-class/
For Class B water meters, the design focus is on achieving a balance between cost, stability, and metering performance in typical residential and commercial water usage scenarios. Therefore, their error standards are primarily set based on actual daily water usage conditions.
Lower Zone (Q1 ≤ Q < Q2):
At low flow rates, due to the reduced fluid driving force, the sensitivity requirements for the meter’s internal measuring mechanism are higher; consequently, the standard allows for a relatively wider error range.
- Maximum permissible error: ±5%.
Upper Zone (Q2 ≤ Q ≤ Q4):
The high-flow range is the water meter’s primary and most common operating range, thus requiring higher measurement accuracy.
Maximum permissible error:
- Water temperature ≤ 30°C: ±2%
- Water temperature > 30°C: ±3%.
3. Maximum Allowable Pressure (MAP)
Maximum Allowable Pressure (MAP) refers to the maximum static water pressure that a water meter can withstand under long-term normal operating conditions without compromising structural safety, sealing performance, or measurement accuracy. Common pressure ratings for Class B water meters currently available on the market include 1.0 MPa and 1.6 MPa.
4. Pressure Loss
The water meter itself creates resistance to water flow, resulting in pressure loss. The ISO 4064 standard defines different pressure loss classes, denoted as Δp. A lower pressure loss class indicates that the water meter has a smaller impact on water flow, which helps maintain water supply pressure at the end of the distribution network.
For Class B (Accuracy Class 2) water meters, within the flow range of Q1 to Q3, the maximum pressure loss typically does not exceed Δp63 (pressure loss class 63, equivalent to 0.063 MPa).
5. Temperature Class
The temperature class for Class B water meters typically follows ISO classifications such as T30 (cold water) or T90 (hot water), depending on the meter design.
6. Size Range
The common size range for Class B water meters is typically DN15 (1/2“) to DN50 (2”). This size range essentially covers the metering needs of most residential, small commercial, and light industrial water supply systems, making it the most widely used specification range for Class B mechanical water meters.
How to Identify a Qualified Class B Water Meter?
By following the criteria below, we can effectively ensure compliance with Class B requirements.
- Require suppliers to provide certification marks compliant with ISO 4064 or GB/T 778-2018. Additionally, check whether the product nameplate or test report clearly states “ISO 4064 Class B” or “Accuracy Class 2,” along with relevant information such as the maximum allowable working pressure and pressure loss class.
- It is essential to require suppliers to provide type test reports or type approval certificates issued by an authoritative third-party laboratory, as these reports serve as core evidence demonstrating that the water meters meet accuracy and durability requirements.
- Selecting a reliable manufacturer is key to ensuring water meter quality. Priority should be given to suppliers that meet the following criteria:
- Hold ISO 9001 quality management system certification, OIML R49 certification, and an ISO 4064 Class B type approval certificate
- Possess many years of manufacturing experience, be familiar with ISO 4064 and GB/T 778 standards, and provide complete technical documentation and test reports
- Allow factory audits, including production line and quality control inspections
- Be able to provide spare parts, technical support, and periodic verification services
FAQ
Is Class B same as Accuracy Class 2?
No, Class B is not exactly the same as Accuracy Class 2 because the two do not adopt the same standard, Accuracy Class 2 utilizes the ISO 4064:2014 standard, whereas Class B utilizes the ISO 4064:1993 standard. However, Class 2 meters correspond to the legacy Class A and Class B meters, and Class B is most commonly associated with Accuracy Class 2 in practice.
Is Class B Still Relevant under Current Standards?
Formally, no. ISO 4064:2014 replaced Class A/B/C/D with Accuracy Class 1 and Class 2. However, “Class B” is still widely used in the market as an informal reference, typically corresponding to Accuracy Class 2.
What Applications are Suitable for Class B Water Meters?
Residential water supply systems
Apartment sub-metering
Small commercial buildings
General water distribution networks with stable flow conditions
How Accurate is a Class B Water Meter?
According to ISO 4064-based performance:
Lower zone Q1≤Q<Q2: ±5%
Upper zone Q2≤Q≤Q4:
±2% for ≤30°C
±3% for >30°C
Are Class B Water Meters Suitable for Low-flow Detection?
They provide moderate low-flow sensitivity but are not ideal for detecting very small leakage flows. For higher sensitivity, Class C (R160) meters are recommended.
