In modern water supply systems, especially those involving high-volume transmission pipelines, large-diameter flow meters play a vital role in accurate water metering. These meters are typically installed at key nodes such as raw water inlets, water treatment plant outlets, and major municipal pipelines. To ensure long-term accuracy and stability, proper installation and equipment selection are critical.

Choosing the Right Flow Meter Technology

Among the mainstream technologies available today, electromagnetic flow meters and ultrasonic flow meters are most widely used for large-diameter metering. Each has its strengths:

Because the two technologies rely on different flow measurement principles, the best practice for critical pipelines is to install both meters in series. This dual-technology method allows mutual verification and enhances confidence in data accuracy.

➡ Learn more about our electromagnetic flow meter solutions
➡ Explore our ultrasonic flow meter range

Why Straight Pipe Length Matters

Both electromagnetic and ultrasonic meters are velocity-based. They assume a fully developed turbulent flow profile. However, bends, valves, and pumps upstream or downstream can disrupt the flow field, introducing significant errors.

Standard practice:

• Minimum straight pipe length should be 5× to 10× the pipe diameter upstream and 3× to 5× downstream.
• When conditions allow, the longer the straight pipe sections, the better.

Ignoring these principles, or treating the minimum requirements in the manual as maximum limits, is a common installation mistake that results in long-term metering deviation.

Safety Distance from Valves and Pumps

Valves—especially when partially open—can generate flow disturbances. The safety distance between the flow meter and any nearby valve or pump should be adjusted based on field testing or conservative engineering judgment. Ideally, avoid placing meters immediately downstream of such components.

Conclusion

The "install once, use for life" principle applies to large-diameter meters. That’s why installation accuracy and planning are as important as the device itself. Installing a combination of electromagnetic and ultrasonic flow meters in series, ensuring adequate straight piping, and avoiding high-disturbance zones will significantly enhance long-term measurement reliability.