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A Thermal Imaging Based Wireless SensorNetwork for Automatic Water Leakage Detection in

Distribution PipesRakhel Kumar Parida,Vidhya Thyagarajan,Sreeja Menon

Rambus,Inc.Bangalore,India

{rkparida,vidhya,smenon}@rambus.com

Abstract—Water leakage is a significant problem in bothdeveloping and developed countries causing water loss in water-distribution systems. Leakage causes economic loss in the formof wastage of water, damage to pipe networks and foundations ofroads and buildings, and also poses risk to public health due towater contamination. The lost or unaccounted amount of wateris typically 20-30 percent of production. Some older systemsmay lose even up to 50 percent. The water pipe networks inhouses as well as public places are generally concealed and hencedetecting water leakage in the initial stages before an upcomingdamage is difficult. The existing technologies for detecting leakagehave various limitations such as efficiency being dependent onsize, material and depth of pipes, need for manual intervention,dependency on weather and surface conditions and effect ofwater pressure. In this paper, we propose an automated waterleakage detection system using a wireless sensor network createdalong the distribution pipes based on thermal (IR) imaging.Thermal imaging has the capability to work in low lighting ordark conditions and helps in capturing the contrast betweenhot and cold areas created due to water leakage. A networkof low cost, low power thermal imaging sensors each having itsown processing and Radiofrequency (RF) Transreceiver units andoperating independent of pipe, weather or surface conditions isproposed in this paper. A central database is updated on a real-time basis, enabling very early leakage detection and initiatingsubsequent action to address the problem. An example systemevaluation is performed and results highlighting the power andcost impact of the sensor network system are presented.

Index Terms—Automatic water leakage detection, Water dis-tribution pipe, Thermal imaging, Wireless sensor network

I. INTRODUCTION

In today’s water distribution systems, a significant percent-age of water loss happens while in transit from treatmentplants to consumers. According to an inquiry made in 1991by the International Water Supply Association (IWSA), theamount of water lost or ”unaccounted for” is typically inthe range of 20 to 30% of production [1]. Unaccounted forwater is usually attributed to several causes including leakage,metering errors and theft, of which leakage is found to be themajor cause. Leaks can happen due to several reasons suchas corrosion, material defects, faulty installation, excess waterpressure, ground movement caused by drought or freezing,and excessive loads and vibration from road traffic [2]. Inaddition to environmental and economic losses caused byleakage, leakage in pipes also pose public health risk since

leaks are potential entry points for contaminants if a pressuredrop happens in the system [3].

Economic pressure, concern over public health risk andthe need to conserve water motivate water system operatorsto implement leakage control programs. Early detection ofleakage will result in saving a significant amount of water.In this paper, we propose a wireless sensor network systembased on thermal (IR) imaging which can be deployed withdistribution pipes to achieve the goal of early leakage detectionand prevention of associated damage.

In this paper, we make the following contributions.• Define a thermal(IR) imaging system that can be de-

ployed with water distribution pipe networks making useof the contrast in thermal image created due to waterleakage.

• Propose a wireless sensor network system which con-nects the thermal imaging systems to perform real time,automated leakage detection and communication to acentral database.

• Perform an evaluation of the system considering powerand cost factors.

The rest of the paper is organized as follows.Section II describes related work in the area of water leakagedetection and their associated limitations.Section III describes the principle of thermal imaging.Section IV describes our proposed thermal imaging basedsensor network scheme for water leakage detection.Section V describes the result of the system evaluation onthe basis of cost and power consumed.

II. RELATED WORK

The following are some techniques used for water pipeleakage detection.

A. Listening Device

Listening devices as shown in Figure 1a use the acousticmethod of leak detection. Sound waves are detected by trans-ducers which convert mechanical waves to electrical signals.The electrical signals are then processed and the resultant root-mean-square (RMS) voltages are tracked. An increase in thesevoltage levels is relied upon to indicate the onset and growth

IEEE CONECCT2013 1569679473

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(a) Listening Device (b) Leak Noise Corre-lators

(c) Tracer Gas Tech-nique

(d) Thermography (e) Ground Penetrat-ing Radar

Fig. 1: Existing Water Leakage Techniques

of a leak. This method of leak detection is performed by afield technician using ground microphones [4].

Limitations:• This technique is affected by attenuation of sound waves

and inaccessibility of desired sensor locations• The technique depends on the experience and ability

of field technicians to determine leak noise from otherbackground noises.

• Efficiency of technique is dependent on type of soil,material and depth of the pipe.

• To be effective, ground surface listening devices needto be almost directly over a leak location and hence isnot practical for long, large diameter water transmissionpipelines.

B. Leak Noise Correlators

Correlators as shown in Figure 1b are acoustic sensorsattached to pipeline appurtenances. They work on the principleof detecting a noise and measuring the transmission speedof that noise along the water pipe using hydrophones oraccelerometers. Data from either the accelerometer sensorsor the hydrophones are generally transmitted to a correlatorunit using wireless radio transmitters. By deploying a crosscorrelation function, the noise correlator determines the timelag between measured leak signals. The location of the leakis determined relative to one of the measured points and iscalculated based on an algebraic relationship of the time lag,distance between the points, and sound propagation velocitywithin the pipe [5].

Limitations:

• Correlators are dependent on size and material of pipes.They are less effective in larger diameter pipelines andpipes made of concrete,PVC and GRP.

• The correlators have to be moved frequently to monitoralong the length of long pipelines.

C. Tracer Gas

The tracer gas technique as shown in Figure 1c consists ofinjecting a gas (helium or a mix of hydrogen and nitrogen) intothe water network under pressure. The water which escapesat the leak point also contains the gas and is detected by aspectrometer. This technique is not dependent on nature ofsoil and material of pipe and has direct access to the pipe [6].

Limitation: This technique requires external gas injectioninto the pipe network.

D. Thermography

Thermography shown in Figure 1d makes use of thermal(IR) camera to measure and image the emitted infrared radi-ation from an object. The principle behind the use of thermalimaging for leak detection is that water leaking from an under-ground pipe changes the thermal characteristics of the adjacentsoil. Infrared cameras can be used to detect this change inthermal characteristics and can detect thermal contrasts onpavement surface due to water leaks. Thermography enablesrelatively large areas to be monitored in less time and withless cost. It is also independent of pipe type and size and canbe used in day or night time [7].

Limitations:• Thermography is dependent on weather conditions, soil

and pavement conditions.• The technique depends on ground water level and dis-

tance between sensor and source (As distance of sensorfrom surface increases, thermal contrast improves).

• Nearly 40% of water leaks infiltrates into adjacent sewerpipes preventing moisture movement to surface, whichfails the thermal imaging based detection.

E. Ground Penetrating Radar

Ground-penetrating Radar (GPR) shown in Figure 1e canidentify leaks in buried water pipes. GPR works either bydetecting underground voids created by the leaking water whenit circulates near the pipe or by detecting anomalies due tosoil saturation with leaking water. The potential of ground-penetrating radar for is independent of the type of the pipeand can be applied to both metallic and plastic pipes [8].

Limitations:• Not suitable for long pipe lengths as the device has to be

carried by an operator along the length of the pipe.• The technique is not effective in highly conductive clay

and silty soils.• Inconsistency in water pressure causes noisy measure-

ments.• The GPR antenna beam width is broad making it difficult

for the radar to discriminate between closely spacedpipes.

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III. THERMAL IMAGING TECHNIQUE

Thermal Imaging is an imaging technique based on thedifference of temperature of imaged objects. A special lensfocuses the infrared light emitted by all of the objects inview. The focused light is scanned by a phased array ofinfrared-detector elements. The detector elements create a verydetailed temperature pattern called a thermogram in about one-thirtieth of a second. This information is obtained from severalthousand points in the field of view of the detector array.They can sense temperatures ranging from -4 to 3600 degreesFahrenheit, and can normally detect changes in temperature ofabout 0.4 degree Fahrenheit [9].

In the Thermographic technique described in Section II-D,thermal imaging is performed by imaging the change inthermal characteristics of soil adjacent to the leaking pipes.The technique thus has limitations due to dependency onsoil and weather conditions and requirement for moisture topenetrate to the surface. In our proposed system of waterleakage, we arrive at thermal imaging as an ideal method fordirectly ’mapping’ pipes that run underground. Leaking pipescan be recognized by irregular heat shapes captured by thedirect thermal image of the pipe by mounting thermal camerason the distribution pipes. Our technique allows for real-timemonitoring of distribution pipes directly and a wireless sensornetwork system interconnecting the thermal imaging systemscan be set up to perform automated leakage detection.

The thermal imaging is additionally useful because of thelack of ambient light in underground pipe systems, which isnecessary for normal imaging. The thermal camera capturesthe contrast between the hot and cold areas on the pipe causeddue to water leakage as shown in Figure 2. Further detailsregarding our sensor network system is provided in Section IV.

Fig. 2: Thermal Imaging for contrast determination

IV. THERMAL IMAGING BASED WIRELESS SENSORNETWORK SYSTEM FOR WATER LEAKAGE DETECTION

A. Overview

In our proposed system, we use both thermal imaging andRF technology to continuously monitor the underground waterdistribution lines and send the information to a central location.

Fig. 3: Distribution System with Thermal Imaging Cameras

As shown in Figure 3 each section of the pipe (housed withina duct) will be equipped with a sensor unit, consisting of athermal imaging camera and a RF Transreceiver. The thermalimaging camera will capture the image periodically, such asonce in a day and with local image processing it will identifyif there is any leakage in that section of pipe. Subsequently,using the RF Transreceiver the detected information is sent tothe central base station. Subsequent sections below describethe scheme in detail.

B. System Components

Figure 4 shows the components of a sensor unit in ourwireless network system. The major components are thefollowing:

1) Thermal(IR) camera sub-system, which includes thethermal imaging camera, sensor and read-out circuitry.

2) RF transreceiver sub-system, which includes an antennaand transreceiver chip.

3) Microprocessor, which performs image processing andstores the status information related to water leakage aswell as operational status of the sensor components.Theprocessor also monitors real time and initiates the vari-ous commands such as power management control andimage capture on programmed periodic intervals. Themicroprocessor has a non-volatile memory for storingcommands as well as data so that data can be preservedeven when the processor is in low power/power off state.

Fig. 4: Sensor System Components

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Each sensor unit can monitor an area under the line of visionof the IR camera, typically in the order of several hundreds ofmeters [10]. A wireless network is established between a seriesof such sensor units using the embedded RF Transreceiver [11][12] and antenna communicating with a central base station.The sensor units are designed using low power componentsto be self-sufficient and consume very little power to have abattery life of several years.

C. Initial Set Up and Operational Mechanism

Figure 5 shows an overview of the initial setup and opera-tion of the system.

1) Initial Set Up: The following initial set up is to beperformed for implementing the proposed wireless sensornetwork as depicted in Figure 5.

• The distribution pipes have to be housed within a ductmade of material such as plastic. The duct should beconstructed to provide clearance of around 1cm betweenthe pipe and the duct in order to assist in the IR imaging.

• The leakage monitoring sensor units as described inSection IV-B are installed along the water distributionpipe. The installation of duct and sensor units can bedone during initial installation or during maintenanceoperations.

• A base station is required to be set up at ground levelwhich receives the information from the sensor networkperiodically and can infer the status of underground pipenetwork. Action to fix leakages can be initiated at anearly stage from the base station. The base station shouldalso be capable of transmitting information to the sensorunits in the network and perform the initial programmingof the microprocessor in each of the sensor unit in thenetwork for various control parameters.

2) Operational Mechanism: As shown in Figure 5, theoperational mechanism of the proposed sensor network hasthree stages. In order to maximize power savings, the thermalcamera sub-system and the RF transreceiver sub-system arepowered off by default and are in power on mode only forfew seconds in a day. The microprocessor works in a lowpower mode by default wherein the real time clock is runningand at programmed intervals, returns to fully active mode toexecute the required functions.

Thermal Camera SubSystem Operation: The micropro-cessor is programmed to wake up the thermal camera sub-system at programmed periodic intervals (say, once in a day).A new thermal image is taken and the image is passed tothe microprocessor. The microprocessor which is now in fullyactive state, performs simple image processing such as edgedetection techniques to determine if there is a water leakagein the imaged zone or not. This status information is stored inthe registers in the non-volatile memory of the microprocessor.Additionally, status information regarding capture of newimage, transferring of image to microprocessor is also capturedin the microprocessor. The processor then powers down thethermal camera sub-system until the next monitoring period.

Fig. 5: System setup and Operation Overview

RF Transreceiver SubSystem Operation: After comple-tion of thermal camera subsystem operation, the micropro-cessor powers up the RFTransreceiver subsystem based onprogrammed periodic interval. The RF circuit then transmitsown sensor information to the next sensor unit and status fromprevious unit, if available through the transreceiver chip andantenna following a standard protocol such as Zigbee [13]. Thestatus of various operations, such as receipt of status from theprevious unit, successful transmission of own information tonext unit etc. are also recorded in the micro-processor. Theprocessor subsequently powers down the transreceiver sub-system until the next monitoring period.

Maintenance Operation: The base station can also performmaintenance operations of the sensor network, such as mod-ifying and/or monitoring the transmission timings, check theworking status of the various components etc. For this, the basestation initiates commands targeting individual sensor units orbroadcasts to all units seeking the respective status informationor updating the programmable timer settings.

Advantages: The following are the advantages of ourproposed sensor network:

• Real time, Automated water leakage detection and hencedoes not need manual inspection.

• Very early detection of leakage is possible.• Efficiency of the system is not dependent on the material

or size of the pipe as well as surface or weather condi-tions.

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V. SYSTEM EVALUATION

This section comprises of the detailed evaluation of ourthermal imaging based wireless sensor network system con-sidering two important system parameters:

• Power : Power consumed by the system components asshown in Figure 4 in each sensor unit in the wirelessnetwork is analyzed considering both active and idlemode power. Power is calculated in terms of battery lifefor each component and subsequently the battery life forthe entire system is arrived at.

• Cost : Cost incurred by all the system components in eachsensor system in the wireless network as well as the outerduct of the pipe and base station is calculated in order toarrive at the cost estimate of the proposed system.

A. System Considerations

The following considerations are made to perform theevaluation of the sensor system.

1) Battery: Four general purpose AA batteries each with 1.5V operating voltage and battery capacity of 500mAh areconsidered. The total battery capacity is thus 3000mWh[14].

2) MicroProcessor: A STM32L microcontroller with flashmemory for storing data is considered with active powerconsumed =0.8mW and idle power=1uW [15]. Themicroprocessor is considered to be powered on for 10minutes and powered off for rest of the day.

3) Thermal Camera: Commercially available light weightlow power thermal imaging camera like MIRICLE Mi-croCam is considered with power consumption of 0.6Wand achievable imaging distance of 100m [16]. Thecamera is considered to be powered on for 10 secondsin a day.

4) RFTransreceiver: Low power ZigBee standard RF tran-sreceiver is considered with power consumption of theorder of 16mW [17]. The RF transreceiver is consideredto be powered on for 1 minute in a day.

B. Evaluation Summary

Table I gives the power consumed by the various compo-nents of the sensor system.

• Considering the battery capacity of 3000mWh and thetotal power consumption of the sensor unit as 2.02mWhper day, the battery life for sensor system is obtained as1485 days which is around 4 years.

• Cost incurred by city adminstrations for leakage controlin water distribution networks is huge. For example, con-sidering a water distribution network which is 26000km

TABLE I: System EvaluationSensor Unit Active

Power(mWh)IdlePower(mWh)

Thermal Camera 1.67 0Microcontroller 0.13 0.02RFTransreceiver 0.27 0Total 2 0.02

long running through city of Tokyo, the administrationcurrently spends around 50 million dollar per year forleakage control activities using prevalent leakage detec-tion techniques [18]. With the imaging distance of anIR camera as 100 m, around 250000 sensor units wouldbe required with our wireless sensor network system tocover the same area as in the example. Considering theprices of each of the components in the sensor systemand cost of the external duct of the pipe network [19][20] [21] [22], the cost of the system is estimated to beapproximately 20 dollars/km and the total cost to be 5million dollars. With this one time installation cost, thenetwork would be set up with a low cost and reliable wayfor early stage leakage detection and also would provideadditional savings by preventing water leakage.

VI. CONCLUSION

In this paper, we highlighted the importance of early waterleakage detection and studied the various prevalent techniquesfor detecting the leakage. We introduced a thermal imagingbased sensor system to be deployed with water distributionnetworks making use of the contrast in thermal image createddue to water leakage. A wireless sensor system connectingthe thermal imaging systems to a central base station wasintroduced in the paper to perform real time, automatedleakage detection. An example evaluation of the system wasdone for analyzing the power and cost impact and results wereprovided. We were able to define a low cost, low power waterleakage detection system providing automatic, early detectionindependent of the characteristics of the distribution pipes orweather conditions.

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