Selecting a flow meter for a municipal water or wastewater network involves more than picking a size and a brand. The right meter for a bulk supply main looks different to the right meter for a pump station, a DMA boundary point, or a wastewater treatment plant influent.
Electromagnetic (mag) flow meters are the dominant type in NZ municipal water and wastewater networks. High accuracy (±0.5% or better), no moving parts, suitable for water and wastewater, available from 25mm to 2000mm, wide range of communication outputs, and no pressure drop. For most municipal applications, a mag meter is the default starting point.
Ultrasonic flow meters come in two configurations: inline (high accuracy for clean water, like a mag meter) and clamp-on (transducers clamped outside the pipe, no pipe penetration, ideal for large diameter mains above 400mm).
Mechanical (turbine) flow meters are increasingly uncommon in new municipal installations due to higher maintenance requirements and shorter verification intervals. May still be found in older networks.
Flow meter sizing is based on flow velocity through the pipe, not simply the pipe diameter. You need to know pipe internal diameter, minimum/normal/maximum flow rates, and whether the pipe runs full at all times. NZ Flow Group will size meters correctly for your application.
Standard mag meters need a length of straight, uninterrupted pipe both upstream and downstream to measure accurately. In municipal settings this isn't always available, particularly close to an elbow, tee, or pump station where space is limited. For these situations, zero:zero (0:0) mag meters are available, which don't require the usual straight pipe runs. Manufacturers achieve this with different internal flow-conditioning techniques, making zero:zero meters a practical option when a standard installation isn't feasible.
Bulk supply and billing meters: ±0.5% or better. Network monitoring: ±1–2%. Wastewater and effluent: ±1–5% depending on application.
Common output options: 4–20mA (analogue, widely compatible), Pulse output (simple and reliable), MODBUS RTU/TCP (digital, enables SCADA diagnostics), HART (digital over 4–20mA), Profibus/Profinet (process control environments). Confirming the protocol before specifying a meter avoids costly integration issues.
All meter types, mag, ultrasonic, and mechanical, are verified every 5 years. Standardising on fewer meter brands reduces spare parts complexity and ensures local support is available when issues arise.
Electromagnetic (mag) flow meters, high accuracy, no moving parts, low maintenance, available in sizes to suit most network applications.
Very important for standard mag meters. Insufficient straight run, caused by bends, valves, or fittings too close to the meter, can cause flow profile disturbances that significantly affect accuracy. Typical requirements: 5–10 pipe diameters upstream, 3–5 downstream. Where space doesn't allow for this, zero:zero (0:0) mag meters are available, which don't require the usual straight pipe runs.
Yes, including clamp-on ultrasonic meters for very large pipes where inline installation is impractical or expensive. Contact us with your pipe size and application details.
MODBUS RTU/TCP is widely used in NZ municipal SCADA and provides rich diagnostic data. 4–20mA with pulse output is simpler and works with most legacy systems. Contact us with your SCADA details for advice.
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