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Good Water Management Saves R3.3 million a Year

Case Study

Good Water Management Saves R3.3 million a Year

An Isoil battery powered mag flow meter with built-in logging was installed in July ’15 and leak detection/repair and rationalization programs were set in motion.Rationalization and repairs were completed on 7 August.

The average flow rate before 7 August was 149 m3/h. After repair and rationalization the flow rate averaged 72 m3/h. This is a saving of 77 m3/h.

Costing the water at R5.00 per m3, there is a cash saving of R385.00 per hour which translates into savings of R277,200.00 per month.

This is an excellent example of how accurate flow measurement together with flow logging informs you what is happening within your network, alerting you to leaks or other problems. The benefits of good water management are clearly proved.

CaseStudygraphGood Water Management Saves R3.3 million a Year


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Isoil Mag Flow Meters - Battery Powered, “Smart”

Isoil Mag Flow Meters - Battery Powered, “Smart”

Battery powered mag meters are ideal for water distribution applications as they are accurate, they don’t under-read as mechanical meters do, and they form part of an Automatic Meter Reading system which also assists with Water Loss management and No Drop assessment and compliance. Battery life is typically 3 to 6 years.

Advantages of Isoil Battery Powered Mag Meters Over Mechanical Meters

The water industry has traditionally used mechanical meters which are especially handy when no power is available.

In 2007 Isoil introduced their battery powered mag flow meter which has major advantages over mechanical meters:

  • Typical accuracy of ± 0.4% compared to ± 2% to ± 5%for mechanical meters.
  • Mechanical meters invariably under-read as they get older due to wear and tear, damage and blockage by foreign bodies and debris. So with mechanical meters you end up giving away water for free! Magnetic meters do not under-read as they get older.
amr 1Mechanical meter body showing build-up of corrosion and debris
vane4fMechanical meters are calibrated by adjusting a vane which affects the angle of impact of the water on the propeller blades.
PlasticlighterEven a small piece of debris can wedge in the turbine and cause the meter to under-read. In this picture you see a piece of plastic which has almost welded itself on to the vanes
PebblesfYou can imagine how pebbles wedged in the meter’s input structure will play havoc with the angle of the water flow and severely affect its accuracy.
gpaphic keys 3Mag meters at Isoil factory – no obstruction to flow.
amr 3Damaged mechanical meter vanes

The Accuracy challenges caused by stones and debris strongly effect the meter’s accuracy while it is installed. However when the internals are removed for checking and calibration, the debris, stones and foreign bodies are removed – so accuracy in the workshop will much better than in the field! In our experience from carrying out many field checks of mechanical meters using our portable ultrasonic flow meter, we have found that most mechanical meters are under-reading by amounts varying from -1.5% to -100% i.e. the meter not turning at all. So the accuracies found in the workshop give a misleadingly positive picture when compared to the mechanical meters' accuracy in operation!

  • It is good practice to install a filter up-stream of a mechanical meter, in an attempt to prevent damage to the meter. These filers clog and they are seldom cleaned. So pressure drop and flow obstruction increases. Mag meters do not require filters.
  • Mag meter’s bore is the same as the pipe so there is no obstruction – so it is not vulnerable to damage and does not cause a pressure drop and does not reduce the line’s flow capacity.
  • Low maintenance leading to low costs and minimal downtime.
  • With mechanical meters you typically take a totaliser reading once a month and you have no idea of flow patterns. With the battery powered mag meter you log flow rate at 15 minute intervals and so get a full understanding of your network operation.
  • Optional pressure sensors.
  • Display LCD for flow rate, forward, reverse and net flows and pressure (optional).
  • Battery Powered – typically 3 – 6 years life.

So the Isoil battery powered mag flow meter is a complete, more accurate and more reliable replacement for mechanical meters which can pay for itself by not giving water way for free!


“Smart” meters have built-in data loggers and GSM modems which send flow trends and flow totals via the GSM network to a data presentation system. The Isoil mag meter meets this requirement and integrates fully with the N&Z Scada which together produce a tried and tested Automatic Meter Reading system which is widely used in South Africa in water boards, municipalities, mines and agriculture.

Meter Reading reports are automatically e-mailed to users together with Flow Trends, Water Balances, etc.


In addition to the basic function of flow rate monitoring and totalisation, Isoil’s battery powered mag meter has the following features and benefits:

  • Typical accuracy of the full bore flow meter is ± 0.4%.
  • Certified to ISO9001: ISO EN17025: OIMLR49 and MID1001.
  • All flow meters are “wet” calibrated on an ISO17025 approved flow rig.

gpaphic keys 7Every Isoil mag meter is wet calibrated at an ISO17025 approved flow rig

  • Measure flow, volume and pressure in real time.
  • Smart sampling of flow measurement to extend battery life without reducing accuracy of measurement.
  • Low flow calibration functionality without affecting high flow calibration.
  • Display screen for flow rate, volume, etc.
  • Alarms (e.g. empty sensor detection, over-range, etc.).
  • Possible to set the Volume Totalizer, password protected.
  • The flow electronics, data logger, GSM module and batters are all enclosed in a single housing to minimize the risk of vandalism and cable theft.
clamp on time 3
  • IP68 enclosure.
  • Alarm when flow or pressure exceeds a pre-set maximum or minimum.
  • Eliminate possible human error when taking meter readings or entering the readings into the computer.
  • Up to two pressure sensors for measuring line pressure, reservoir level or dam level.

gpaphic keys 4Sensor monitoring line pressure or reservoir level
  • Reservoir Level Management is particularly important in water distribution and we provide full monitoring and management.
  • “Full bore” - in other words Isoil mag meters are the same size as the pipe line so there is no pressure drop or flow rate limitation.
  • Isoil’s insertion battery powered mag flow meter is less accurate than the full bore model but costs less, especially for large pipe lines. With our “hot tap” system it can be installed while the pipe is in use.
  • Corrosion Potential: Water pipe lines in South Africa are partially susceptible to corrosion. Corrosion is the number one cause of leaks and pipe bursts. Isoil’s unique Corrosion Potential module, compatible with the battery powered meter, measures the Corrosion Potential between the pipe and the soil.

pressure hydro 2Reservoir Level Management reservoir 1 topReservoir level trend showing high and low alarms gpaphic keys 5Insertion meter complete with line pressure sensor

gpaphic keys 6Corrosion potential module


Verification is becoming a standard QA requirement to monitor installed bulk flow meters to confirm that key parameters remain within specified tolerances over time. Each meter has its own unique “bench mark” of parameters which are measured when the meter is manufactured or when it is installed. Best operating practise is to re-measure these parameters at specified intervals. N&Z offers verification for the Isoil battery powered flow meter.

Stand-alone verification using the ISOCAL

The Isocal is a stand-alone verificator which is itself certified periodically by the factory and therefore has traceability back to National Standards. The Isocal connects between the Isoil flow sensor and the converter. It executes a large number of tests automatically on the sensor and/or convertor and produces a printed, traceable certificate. Isoil pioneered the verification of battery powered mag meters.

isiol battery powered 4Verifying Isoil battery powered flow meter

verification certificateVerification certificate

Built in Verification (automatically e-mails reports to you)

The Isoil mag meter continuously carries out numerous self-checks. In addition to this Isoil has developed “Built In Verification” (BIV) which includes additional tests. With this option the user selects the frequency of the Built In Verification report. The meter carries out these measurements and automatically e-mails a file which produces a hard copy Verification Report. This functionality is a great contributor to optimized maintenance particularly where there are many meters in different locations which are not easily accessible. So with Built In Verification you get an early warning of when you need to travel to the meter to perform the higher level Isocal verification.

Meter Selection Guide

It is important to select the best size meter for the application. Bearing in mind that pipes are often oversized for their current flow rate, a smaller diameter flow meter could be preferred. Smaller diameter meters cost less and also increase the flow velocity. Although the Isoil flow sensor has an extremely uniform magnetic field making it accurate at lower flow rates, it is still preferable to keep your minimum flow at above 0.1m/sec. Once you know your expected minimum and maximum flow rates you can use the table below to select the flow meter diameter which best suits the operating conditions.

This table applies to normal working conditions. For abrasive fluids chose a larger meter to reduce velocity and thereby reduce abrasion damage. On the other hand if the fluid tends to coat the meter chose a smaller meter to increase velocity and minimize deposits on the electrodes.

The graphs below give the relationship between flow velocity and flow rate for various meter sizes and is also useful for sizing meters.

MeterorPipeSelectionGuide1 Meteror Pipe Selection Guide

Relevant Associated Topics

Water loss management; Reservoir level management; Water quality; Line pressure; Leak detection; Data loggers; Water balance; Water demand management; Water supply management; Water distribution; Flow surveys; Battery powered flow meters; Data logging; Smart loggers; Identification of water leaks and reservoir over flows; Water conservation; Non-revenue water; Infrastructure leak index (ILI); Meter testing; Meter verification; Magnetic flow meters.

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Measure flow in part-filled pipes and open channels without weirs or flumes

Area velocity flow meters are the ideal solution for measuring flow in partially filled pipes and open channels.  Ground water flowing in open channels or part filled pipes is normally metered using weirs, flumes or the Manning formula.  Weirs and flumes frequently erode or silt up making metering misleading.  The Manning formula model is strongly affected by changes in the channel conditions.  Down-stream obstructions also lead to dramatic over-reading by all these metering methods.

Area velocity flow meters are the ideal solution for measuring flow in partially filled pipes and open channels.  Greyline is a world leader in this application and there are many hundreds of Greyline Area Velocity Flow Meters measuring flow in Southern Africa.  Greyline is a leader in all formats of water metering.

How It Works


  • Level is measured by an ultrasonic sensor which can be mounted at the bottom of the channel, externally above the channel, or by a pressure sensor in the channel.
  • Flow velocity is measured by a submerged Doppler sensor which is ideal for most surface water, waste water and effluent applications or alternatively by a non-contract laser sensor which is ideal for waste water and effluent.
  • These measurements, combined with the stored data of the geometry of the channel give volumetric flow rate.

Water flow measurement
Area velocity flow meter
AVFM 001Area velocity flow meter


Open Channel Flow Surveys-Stingray and Mantaray

While the AVFM is used for permanent installations, Greyline offer two portable solutions for site surveys using their proven Area Velocity Flow Metering technology.  The Stingray and Mantaray are battery powered and are therefore ideal for spot checks or battery powered flow trend logging.


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Products and Services
Automatic Meter Reading (AMR)
Water Loss Management
Leak Detection
Reservoir Level Management
Water Quality
Flow Surveys
Data Loggers