How to Choose the Right Electromagnetic Flow Meter for Water and Wastewater in Australia

Choosing the wrong flow meter can turn a simple water measurement point into a maintenance problem. The meter may be the wrong size, the liner may wear early, the display may fail in a flooded pit, or the signal may not suit the control system.

Electromagnetic flow meters, often called mag meters, are a strong fit for water and wastewater because they have no moving parts and can measure dirty, suspended, or corrosive liquid. They work by measuring voltage induced as a conductive liquid moves through a magnetic field. For clean water, sewage, trade waste, recycled water, and process water, that can give stable measurement with low pressure loss.

The key is matching the meter to the pipe, fluid, site conditions, and control system. Here is what to check before choosing an electromagnetic flow meter Australia suppliers can support for local water and wastewater applications.

A correctly selected mag meter starts with the pipe and the process.

Start with the application and fluid

An electromagnetic meter only works with conductive liquid. That makes it suitable for most water and wastewater duties, but not for oils, fuels, gases, steam, or very low-conductivity liquids.

Common applications include:

• Potable water transfer

• Bore water and raw water intake

• Recycled water

• Irrigation supply

• Sewage pumping mains

• Wastewater treatment inlet and outlet lines

• Trade waste discharge

• Chemical dosing lines where the liquid is conductive

  
  

For a clean water flow meter, the main priorities are usually accuracy, approvals, pressure rating, and communication with the control system.

For a wastewater flow meter, the priorities shift. The meter must handle solids, grit, ragging risk, coating, chemical attack, outdoor installation, and possible flooding.

Before looking at models, write down the basic service conditions:

• Liquid type

• Minimum, normal, and maximum flow rate

• Pipe size and material

• Pressure and temperature

• Conductivity

• Solids content

• Chemical exposure

• Installation location

• Required signal output

• Flange standard

• Power supply

  
  

That list will remove many unsuitable options before price enters the discussion.

Match the meter size to pipe diameter and flow range

Pipe diameter is the obvious starting point, but it should not be the only sizing factor. A mag meter is usually selected to match the nominal pipe size, such as DN50, DN100, or DN300. This keeps installation simple and avoids reducers.

The flow range must also suit the meter’s velocity range. Most electromagnetic meters perform best when the liquid velocity sits inside the manufacturer’s recommended limits. Very low velocity can reduce signal strength and make readings less stable. Very high velocity can increase liner wear, noise, and pressure effects.

As a practical guide:

Application	Typical sizing goal	Why it matters
Potable water	Stable velocity across normal demand	Improves accuracy and low-flow reading
Wastewater	Enough velocity to keep solids moving	Reduces settlement and coating
Pumped mains	Check minimum and maximum pump flow	Avoids oversizing the meter
Batch filling	Choose for the real dosing range	Supports repeatable totals
Gravity-fed lines	Confirm the pipe stays full	Mag meters need a full pipe

A common mistake is choosing a meter only because it matches the existing pipe. If the pipe is oversized and normal flow is low, the meter may spend much of its life near the bottom of its measurable range.

For new installations, it can make sense to use reducers and install a smaller meter body, as long as pressure loss, access, and maintenance needs are acceptable. For existing sites, confirm that the pipe will remain full at the measurement point. A partially filled line can give false readings even when the electronics are working correctly.

Choose the right liner for water and wastewater

The liner protects the inside of the meter body and electrically insulates the fluid from the tube. Liner selection affects chemical resistance, abrasion resistance, temperature limits, and service life.

Common liner materials include hard rubber, soft rubber, PTFE, PFA, EPDM, and polyurethane. Manufacturers use different names and grades, so always compare the chemical and temperature ratings on the datasheet.

Liner material	Often used for	Key benefit
Hard rubber	Water, raw water, many wastewater duties	Good general-purpose choice
Soft rubber	Water and mildly abrasive fluids	Good flexibility and wear resistance
EPDM	Potable water and general water service	Good water compatibility
PTFE or PFA	Chemical or corrosive service	Strong chemical resistance
Polyurethane	Slurries and abrasive wastewater	Good abrasion resistance

For potable water, check whether the liner material is suitable for drinking water service under the relevant project requirements. For wastewater, look closely at grit, sand, and suspended solids. A liner that performs well in clean water may not be the best choice for abrasive sludge or stormwater with sediment.

Chemical exposure also matters. Trade waste may include cleaning chemicals, acids, alkalis, salts, or solvents. If the waste stream varies, be conservative and provide the supplier with the worst-case composition.

The liner and electrodes are in constant contact with the liquid.

Select electrode materials for the liquid chemistry

Electrodes make contact with the liquid and pick up the induced voltage. If the electrode material is wrong, the meter can suffer from corrosion, coating, unstable signal, or early failure.

Common electrode materials include:

• 316L stainless steel

  Often used for clean water, potable water, and many general wastewater applications.

  
  

• Hastelloy

  Often selected for more aggressive wastewater or chemical exposure, depending on the chemistry.

  
  

• Titanium

  Used where chloride resistance suits the application, subject to the actual process conditions.

  
  

• Tantalum

  Used for some highly corrosive acids, but it is usually a specialist and higher-cost choice.

  
  

Do not select electrodes from a generic preference list. Match them to pH, chloride level, chemical additives, cleaning agents, and temperature. If the site handles trade waste, ask for a chemical compatibility check.

Coating is another issue. Fats, oils, biological growth, and minerals can build up on electrodes. Some meters offer self-cleaning electrode designs, replaceable electrodes, or diagnostics that detect coating. Those features can be useful in wastewater treatment plants and pump stations where access is difficult.

Confirm conductivity before ordering

Electromagnetic meters need minimum liquid conductivity to work. Most water and wastewater applications have enough conductivity, but do not assume.

Potable water, groundwater, recycled water, and sewage usually sit comfortably within typical mag meter requirements. Very pure water, condensate, demineralised water, or some treated process water may not.

Check the meter datasheet for the minimum conductivity, often stated in microsiemens per centimetre. Then compare that with the expected minimum conductivity of the liquid, not just the average value.

Conductivity can change with:

• Source water changes

• Rainfall dilution

• Seasonal treatment changes

• Chemical dosing

• Industrial discharge

• Blending of water streams

  
  

Earthing also affects signal quality. Conductive metal pipework may provide a stable reference, but plastic, lined, or coated pipes often need earthing rings or grounding electrodes. Poor earthing can look like a faulty meter when the real issue is installation.

Check flange standards and pressure ratings used in Australia

Australian water and wastewater assets may use several flange standards. Common project requirements can include AS 4087, AS 2129, AS/NZS-related waterworks specifications, or international standards such as EN, ANSI, or JIS depending on the plant, package equipment, or imported skid.

Do not assume that “DN100 flanged” is enough information. Specify:

• Nominal diameter

• Flange drilling standard

• Pressure class

• Face type

• Gasket type

• Bolt material requirements

• Pipe material

• Coating requirements

  
  

AS 4087 is common in Australian water infrastructure, especially for waterworks applications, but older sites may still use AS 2129 tables. Imported equipment may arrive with PN16, ANSI 150, or other patterns. If the drilling pattern is wrong, installation stops until adaptors or spool pieces are made.

Pressure rating also matters. The meter body, liner, flanges, and gaskets must suit operating pressure, surge pressure, and test pressure. Pumped wastewater mains can see pressure spikes, so design for the real site conditions rather than only normal operating pressure.

Flange standard and pressure class need to match the pipework.

Decide how much accuracy the process needs

Accuracy claims can be confusing because manufacturers state them in different ways. Many mag meters quote accuracy as a percentage of reading, sometimes with conditions such as minimum velocity, full pipe, proper earthing, and a required straight pipe length.

Typical water and wastewater applications may only need reliable totalisation and flow trend data. Custody transfer, dosing control, discharge reporting, and compliance monitoring usually need higher accuracy and better documentation.

Look at these points:

• Accuracy at low flow

  A meter may meet its headline accuracy at normal flow but perform less well near the bottom of its range.

  
  

• Repeatability

  For batching and dosing, repeatability can matter as much as absolute accuracy.

  
  

• Calibration certificate

  Some projects require wet calibration evidence from the factory.

  
  

• Bidirectional measurement

  Some sites need to measure forward and reverse flow.

  
  

• Totaliser resolution

  Make sure the displayed and transmitted total suits reporting needs.

  
  

Also check the installation instructions. Straight pipe runs, valve position, pump turbulence, air entrainment, and grounding can all affect real-world accuracy. A high-accuracy meter installed badly will not deliver high-accuracy data.

Choose the right IP rating for the site

Water and wastewater meters often live in harsh places. A meter may sit in a chamber that floods, a pit with condensation, a coastal site with salt air, or a treatment plant exposed to sun and rain.

The IP rating tells you how well the enclosure resists dust and water ingress. Common ratings include:

Rating	General meaning	Suitable situations
IP65	Protected against dust and water jets	Sheltered plant areas
IP67	Temporary immersion protection	Outdoor or wet areas with splash risk
IP68	Continuous immersion protection under stated conditions	Flood-prone pits or chambers

IP68 does not mean unlimited underwater service in every condition. Check the depth, duration, cable gland requirements, and whether the transmitter, sensor, or both carry the rating.

Cable entries are often the weak point. Use correct glands, seal unused entries, and avoid water tracking down the cable into the enclosure. In pits, a remote display can keep the electronics above flood level while the sensor remains in the pipe.

Choose between integral and remote displays

An electromagnetic flow meter can have an integral transmitter mounted directly on the sensor, or a remote transmitter installed away from the pipe.

Integral display	Remote display
Compact and simple	Better for pits, heat, vibration, or flooding
Lower installation cost	Easier to read and maintain
Fewer cables	Keeps electronics away from harsh conditions
Good for accessible indoor pipework	Better for buried or awkward pipework

Integral displays suit clean, accessible installations such as pump rooms, skid-mounted systems, and sheltered pipe galleries.

Remote displays suit many wastewater and outdoor applications. If the sensor is in a below-ground chamber or a submerged location, a remote transmitter mounted at eye level can make operation far easier.

Check the maximum cable length allowed between sensor and transmitter. Use the cable type specified by the manufacturer, especially for low-level signal cables. Running sensor cables beside high-power motor cables can introduce noise.

Remote displays keep readings accessible when the sensor is in a difficult location.

Specify the signal outputs before installation

Flow meters rarely work alone. They usually connect to a PLC, SCADA system, data logger, telemetry unit, pump controller, or dosing system.

Common outputs include:

• 4–20 mA

  A standard analogue signal for instantaneous flow rate. It is simple, widely supported, and useful for control loops.

  
  

• Pulse output

  Used for totalised volume. Each pulse represents a set volume, such as litres or kilolitres.

  
  

• RS485

  Often used with Modbus RTU for digital communication. It can transmit flow, totals, diagnostics, alarms, and status data.

  
  

Many sites use more than one output. For example, 4–20 mA may feed the PLC for live flow control, while pulse output feeds a totaliser. RS485 may provide diagnostics to SCADA.

Specify these details early:

• Power supply, such as mains or 24 V DC

• Output type and scaling

• Pulse value and pulse width

• Communication protocol

• Cable distance

• Earthing and shielding

• Alarm outputs

• Flow direction settings

• Local display units, such as L/s, m³/h, ML/d, or kL

  
  

For remote assets, low-power options may matter. Some meters suit battery or solar-powered telemetry, but not every mag meter is designed for that duty.

Do not overlook installation conditions

A good meter selection still needs a good installation. The pipe should stay full, the sensor should be correctly earthed, and the meter should be placed away from conditions that cause unstable flow.

Check the manufacturer’s requirements for:

• Upstream and downstream straight pipe lengths

• Installation near pumps, elbows, tees, and valves

• Vertical or horizontal orientation

• Air pocket avoidance

• Full pipe conditions

• Access for removal

• Sun and weather protection

• Cable routing

• Earthing rings or grounding straps

  
  

For wastewater, vertical upward flow is often preferred where practical because it helps keep the pipe full and reduces solids settlement. In horizontal installations, avoid placing electrodes at the very top or bottom of the pipe if the manufacturer gives orientation guidance. This helps avoid air bubbles at the top and sediment at the bottom affecting the electrodes.

A practical selection checklist

Before issuing a purchase order, confirm these items:

• Pipe size and required meter bore

• Minimum, normal, and maximum flow range

• Liquid conductivity

• Liner material

• Electrode material

• Flange standard and pressure class

• Accuracy requirement

• IP rating for the sensor and transmitter

• Integral or remote display

• Output signals, including 4–20 mA, RS485, and pulse

• Power supply

• Earthing method

• Calibration and documentation requirements

• Installation position and straight pipe availability

• Access for maintenance

  
  

If any item is uncertain, pause and clarify it. Guessing usually costs more than checking.

The right choice balances process, site, and signal

A good electromagnetic flow meter is not just the one with the best datasheet accuracy. It is the one that fits the pipe, handles the fluid, survives the location, and sends the right information to the control system.

For clean water, focus on sizing, accuracy, approvals, and integration. For wastewater, give extra attention to liner wear, electrode material, coating risk, IP rating, and display location.

Get the fundamentals right and the meter should become a reliable part of the asset, not another instrument that needs constant attention.