In this study, effects of the combination of meter replacement and active leakage control on real and apparent losses are investigated. Generally, water meter replacement campaigns, SCADA system operation, data analysis studies and physical leak detection activities are carried out by different units in water utilities. Within the scope of this study, the studies carried out by different units of the water utility were carried out in an integrated manner in the same period and the obtained data sets were analysed together. Thus, water losses, which were at the level of 52% in the pilot study area (PSA), were reduced to 35%. When the volumes of water supplied to the system before and after the study are compared, the volumes after the study were decreased. Also, water losses in the PSA have been reduced by 17%.

  • Reducing water losses is not only a revenue problem, it also results in wasting sources.

  • Effects of integrated management techniques on water losses are investigated.

  • The application in this study by different water utilities will contribute to the management of water losses in WDS.

  • The importance of regular active leakage control studies has been proved.

  • As a result of the study, water losses were reduced by 17%.

active leakage management, apparent losses, drinking water networks, economic analyses, real losses

Recently, sustainable management of drinking water resources has become more crucial due to climate change, population increase and industrialization. Therefore, sustainable management of urban water systems, which are vital for management of water resources, has become more important. A large volume of water, around 35% of the water supplied to the distribution systems, is lost in water distribution systems (Farley et al. 2010; Karadirek et al. 2012, Al-Washali et al. 2016).

A standard water balance table which is presented in Table 1 has been developed by IWA in order to accurately assess water losses in different countries. Water losses, which are classified as real and apparent losses, are the difference between the system input volume and volume of authorized consumption. Real losses are due to pipe bursts, pipe cracks and overflows from storage tanks whereas apparent losses are associated with measurement errors of water meters, data handling errors and unauthorized consumption (Alegre et al. 2000; Lambert & Hirner 2000; McKenzie & Seago 2005; Tabesh et al. 2009; Karadirek 2019, 2020). The problem of excessive water losses is common in many countries such as Turkey, where the country average of total water losses is around 50% and apparent losses are estimated to be 20% (Karadirek 2020).

Table 1

Standard IWA water balance (Lambert & Hirner 2000)

System input volume (SIV) Authorized consumption (AC) Billed authorized consumption Billed metered consumption Revenue water 
Billed unmetered consumption 
Unbilled authorized consumption (UAC) Unbilled metered consumption Non-revenue water (NRW) 
Unbilled unmetered consumption 
Water losses Apparent losses (AL) Unauthorized consumption 
Metering inaccuracies 
Real losses (RL) Leakage on transmission and/or distribution mains 
Leakage and overflows at utility's storage tanks 
Leakage on service connections up to point of customer metering 
System input volume (SIV) Authorized consumption (AC) Billed authorized consumption Billed metered consumption Revenue water 
Billed unmetered consumption 
Unbilled authorized consumption (UAC) Unbilled metered consumption Non-revenue water (NRW) 
Unbilled unmetered consumption 
Water losses Apparent losses (AL) Unauthorized consumption 
Metering inaccuracies 
Real losses (RL) Leakage on transmission and/or distribution mains 
Leakage and overflows at utility's storage tanks 
Leakage on service connections up to point of customer metering 
View Large

Strategies and control techniques for water losses have been developed in many parts of the world (Lambert et al. 2002; Kanakoudis et al. 2011). There are four basic intervention tools to control real losses in water distribution systems, which are pressure management, active leakage management, speed and quality of repairs, and pipeline and asset management (Lambert et al. 2002). Dividing water distribution systems into district metered areas (DMAs) and pressure management are helpful tools to control real losses in water distribution systems (Karadirek et al. 2012). DMAs are isolated sub systems, where the amount of water supplied and consumed can be measured (Thornton 2002; Gomes et al. 2013). Thus, monitoring night flows by the help of DMAs can be facilitated to manage real losses (Alkasseh et al. 2013).

There are also four basic methods to control apparent losses in water distribution systems. These are controlling metering inaccuracies and unauthorized consumption, reducing data transfer and analysis errors (Rizzo et al. 2007). In well managed water distribution systems, a vast majority of apparent losses is resulted from water meter inaccuracies (Arregui et al. 2016).

This study is aimed at providing an evaluation for control of water losses by integrating intervention tools of real and apparent losses. For this purpose, a study area was chosen to control water losses by implementing active leakage control and water meter replacement campaign.

Study area

Antalya, which is one of Turkey's largest tourism destinations, is located in a karstic region, where most of the pipe failures in the drinking water network cannot be detected from the surface. Groundwater is the only source to supply water to the Antalya city and approximately 43% of Antalya City's drinking water is supplied from Duraliler facilities (53 wells). Abstracted water from Duraliler wells is pumped to the distribution system after chlorination as there is no need for treatment. Total average daily water production of the Duraliler facility is approximately 270,000 m3/day. In Antalya city, the distribution system has been divided into nine pressure zones to provide water services for the settlements located at varying elevations. Sedir water distribution network, operated independently from the rest of the distribution network of Antalya city, was chosen as the pilot study area (PSA) (Figure 1). The study area is a dense residential area and mainly consists of domestic customers.
Figure 1
Map showing the details of the PSA and Antalya in Turkey.
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Map showing the details of the PSA and Antalya in Turkey.

Figure 1
Map showing the details of the PSA and Antalya in Turkey.
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Map showing the details of the PSA and Antalya in Turkey.

Close modal

The PSA lies in the P6 pressure zone and water abstracted from Duraliler facility is supplied to the region after chlorination. The PSA has a total pipe length of 8019 m and includes different types of pipes such as PVC, HDPE, and steel. Detailed information about the study area is given in Table 2.

Table 2

Detailed characteristics of the PSA

Total length of distribution pipes 8019 m 
Average age of pipes 11 years 
Total number of service connections 395 
Total number of customers 4260 
Maximum and minimum water pressure during operation 4.43 bar–3.20 bar 
Average pressure 3.71 bar 
Maximum and minimum elevation 63 m–52 m 
Number of valves 59 
Total length of service pipes 12,379 m 
Total length of distribution pipes 8019 m 
Average age of pipes 11 years 
Total number of service connections 395 
Total number of customers 4260 
Maximum and minimum water pressure during operation 4.43 bar–3.20 bar 
Average pressure 3.71 bar 
Maximum and minimum elevation 63 m–52 m 
Number of valves 59 
Total length of service pipes 12,379 m 
View Large

The PSA, which was previously divided into a DMA, was tested by implementing zero-pressure test on October 2019 to determine whether the PSA is an isolated sub system. For this purpose, the inlet valve of the PSA was closed, then water pressure and flow rates of the PSA was monitored through the SCADA system, which is available in the region. It was observed that the water pressure and the flow rate dropped to zero (Figure 2).
Figure 2
Flow rates at the entrance of the PSA.
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Flow rates at the entrance of the PSA.

Figure 2
Flow rates at the entrance of the PSA.
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Flow rates at the entrance of the PSA.

Close modal

Furthermore, the selected buildings within the boundaries of the PSA were visited one by one to check whether the water was cut off. During the zero-pressure test, it was determined that the connections were faulty in eight buildings located within the borders of the PSA, and the data were updated in the GIS system. In addition, a manual pressure measurement was carried out in a hospital in the region, and it was observed that the pressure value decreased rapidly. Thus, it was determined that the PSA was an isolated DMA from the rest of the network.

Reactive and proactive leakage management

Detection of water losses in water distribution systems can be carried out by implementing active and passive leakage detection methods. Passive (reactive) leakage control is based on repairing water leaks reported by customers and/or visible on the surface (Shammas & Al-Dhowalia 1993). Active (proactive) leakage control includes the studies carried out by water organizations in order to detect and repair leaks that do not come to the surface (Shammas & Al-Dhowalia 1993; Thornton et al. 2008; Aboelnga et al. 2018). Active leakage control often relies on the detection of leaks, including unreported and background leaks. Active leakage control helps reducing the time required for repairment and is a helpful response tool to control real losses. It is crucial in karstic regions where pipe failures cannot be determined from the surface due to the ground structure. Active leakage control studies were carried out intermittently throughout 2020 in the Sedir DMA. Standard acoustic listening methods have been applied for active leakage control. Severin AQUAPHON A-100 (1 Hz 9950 Hz) device was used for acoustic listening studies. In the same period, reactive water loss management was also carried out with notifications from customers.

Water meter replacement campaign

The total number of customers in the PSA in 2020 was 4260. The approximate age of the customer meters was determined according to the meter brand and type. The customer meter data used in the study were prepared based on the billing data of November 2020. Figure 3 shows the age percentage of existing water meters in the PSA. There are many different brands, models, and ages of meters in the PSA. Evaluation of the data showed that apparent losses in the PSA were predominantly due to meter inaccuracies. In this context, all customer meters in the pilot study area were replaced with multijet-wet chamber (R160) water meters in November 2020.
Figure 3
Age classification of existing water meters in the PSA.
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Age classification of existing water meters in the PSA.

Figure 3
Age classification of existing water meters in the PSA.
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Age classification of existing water meters in the PSA.

Close modal
Pipe bursts may occasionally occur, especially in water distribution networks with high pressure and relatively older pipe ages. These bursts result in interruptions in water supply, required additional costs for repair and damage to nearby properties and infrastructure. Therefore, water utilities try to minimize the occurrences of pipe bursts and search for techniques for detection and localization of bursts. Active and passive leakage control techniques have been utilized to control water losses in distribution networks. In this study, a total of 68 pipe failures was detected by proactive and reactive leakage management techniques carried out in the PSA in the year of 2020. A total of 26 failures was detected in distribution pipes whereas 42 of total failures were detected in service connections up to water meters. Locations of pipe failures detected and repaired in 2020 are given in Figure 4.
Figure 4
Locations and types of pipe failures in the PSA.
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Locations and types of pipe failures in the PSA.

Figure 4
Locations and types of pipe failures in the PSA.
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Locations and types of pipe failures in the PSA.

Close modal

Furthermore, existing water meters have been replaced to control apparent losses in the PSA.

As a result of the integrated water loss management strategies carried out in the PSA, flow rates and water pressures at the entrance of the PSA were analysed (Figure 5).
Figure 5
Flow rates and water pressure levels at the entrance of the PSA.
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Flow rates and water pressure levels at the entrance of the PSA.

Figure 5
Flow rates and water pressure levels at the entrance of the PSA.
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Flow rates and water pressure levels at the entrance of the PSA.

Close modal

Minimum night flow (MNF) analysis was carried out in the PSA. The MNF of the PSA was around 87 m3/h before water loss control studies started. As active leakage control studies were implemented in June 2020, the MNF value started to decrease down to 76 m3/h. Then an increase was observed in MNF rates as new bursts occurred. In the meantime, active and passive leakage control studies were carried out and a water meter replacement campaign was started. As water distribution systems are dynamic systems, active and passive leakage control studies should be carried out regularly. At the end of the study period, MNF rates of the PSA were observed around 65 m3/h. Average MNF rates before the studies started were around 87 m3/h whereas average MNF rates were reduced up to 65 m3/h. An average water saving of 22 m3/h was achieved by implementing active and passive leakage control and the water meter replacement campaign. The rate of water losses has been reduced from 52% down to 35% by implementing integrated water loss management strategies. Standard water balance tables of the PSA are presented in Tables 3 and 4. Unbilled unmetered consumption is the water that is connected to the network by the water administration but is not metered and therefore not billed within the knowledge of the administration. It basically consists of the amount of water used from parks, fire hydrants, water discharged during the maintenance of pipelines and armatures etc.

Table 3

Standard water balance of the PSA before study (for 11 months)

System input volume (SIV) 139,734 m3/year
100% 		Authorized consumption (AC) 412,648 m3/year
48.47% 		Billed authorized consumption 404,063 m3/year
47.46% 		Billed metered consumption 404,063 m3/year
47.46% 		Revenue water 404,063 m3/year
47.46% 
Billed unmetered consumption 0 m3/year
0.00% 
Unbilled authorized consumption (UAC) 8585 m3/year
1.01% 		Unbilled metered consumption 220 m3/year
0.03% 		Non-revenue water (NRW) 447,347 m3/year
52.54% 
Unbilled unmetered consumption 8365 m3/year
0.98% 
Water losses 438,762 m3/year
51.53% 		Apparent losses (AL) 145,080 m3/year
17.04% 		Unauthorized consumption 21,285 m3/year
2.50% 
Metering inaccuracies 123,794 m3/year
14.54% 
Real losses (RL) 293,682 m3/year
34.49% 		Leakage on transmission and/or distribution mains 289,295 m3/year
33.98% 
Leakage and overflows at utility's storage tanks 4388 m3/year
0.52% 
System input volume (SIV) 139,734 m3/year
100% 		Authorized consumption (AC) 412,648 m3/year
48.47% 		Billed authorized consumption 404,063 m3/year
47.46% 		Billed metered consumption 404,063 m3/year
47.46% 		Revenue water 404,063 m3/year
47.46% 
Billed unmetered consumption 0 m3/year
0.00% 
Unbilled authorized consumption (UAC) 8585 m3/year
1.01% 		Unbilled metered consumption 220 m3/year
0.03% 		Non-revenue water (NRW) 447,347 m3/year
52.54% 
Unbilled unmetered consumption 8365 m3/year
0.98% 
Water losses 438,762 m3/year
51.53% 		Apparent losses (AL) 145,080 m3/year
17.04% 		Unauthorized consumption 21,285 m3/year
2.50% 
Metering inaccuracies 123,794 m3/year
14.54% 
Real losses (RL) 293,682 m3/year
34.49% 		Leakage on transmission and/or distribution mains 289,295 m3/year
33.98% 
Leakage and overflows at utility's storage tanks 4388 m3/year
0.52% 
View Large
Table 4

Standard water balance of the PSA after study (for two months)

System input volume (SIV) 139,734 m3/year
100% 		Authorized consumption (AC) 90,295 m3/year
64.62% 		Billed authorized consumption 88,734 m3/year
63.50% 		Billed metered consumption 88,734 m3/year
63.50% 		Revenue water 88,734 m3/year
63.50% 
Billed unmetered consumption 0 m3/year
0.00% 
Unbilled authorized consumption (UAC) 1561 m3/year
1.12% 		Unbilled metered consumption 40 m3/year
0.03% 		Non-revenue water (NRW) 51,000 m3/year
36.50% 
Unbilled unmetered consumption 1521 m3/year
1.09% 
Water losses 49,439 m3/year
35.38% 		Apparent losses (AL) 12,523 m3/year
8.96% 		Unauthorized consumption 3493 m3/year
2.50% 
Metering inaccuracies 9029 m3/year
6.46% 
Real losses (RL) 39,919 m3/year
26.42% 		Leakage on transmission and/or distribution mains 36,422 m3/year
26.07% 
Leakage and overflows at utility's storage tanks 494 m3/year
0.35% 
System input volume (SIV) 139,734 m3/year
100% 		Authorized consumption (AC) 90,295 m3/year
64.62% 		Billed authorized consumption 88,734 m3/year
63.50% 		Billed metered consumption 88,734 m3/year
63.50% 		Revenue water 88,734 m3/year
63.50% 
Billed unmetered consumption 0 m3/year
0.00% 
Unbilled authorized consumption (UAC) 1561 m3/year
1.12% 		Unbilled metered consumption 40 m3/year
0.03% 		Non-revenue water (NRW) 51,000 m3/year
36.50% 
Unbilled unmetered consumption 1521 m3/year
1.09% 
Water losses 49,439 m3/year
35.38% 		Apparent losses (AL) 12,523 m3/year
8.96% 		Unauthorized consumption 3493 m3/year
2.50% 
Metering inaccuracies 9029 m3/year
6.46% 
Real losses (RL) 39,919 m3/year
26.42% 		Leakage on transmission and/or distribution mains 36,422 m3/year
26.07% 
Leakage and overflows at utility's storage tanks 494 m3/year
0.35% 
View Large

While physical water losses refer to the water that is physically lost before the water reaches the user, apparent water losses are the sum of the losses in which the water is actually used but cannot be compensated by the municipalities/water organizations (Al-Washali et al. 2016). Reducing apparent water losses provides short-term increases in water services/municipal revenues, and these increases allow users to receive better service in the long run (Karadirek 2020). Metering inaccuracies refers to all types of errors associated with the manufacture of meters, and the water consumption due to errors caused by the age, model, type of meters, as well as data processing errors (meter reading and billing). Metering inaccuracies can be determined for administrations that have meter repair and control stations, based on their general calibration experience and data records, while administrations without repair stations use measurement and adjustment legislation, manufacturer information etc. The recommended value for metering inaccuracies in Turkey is between 3 and 20% of the sum of billed metered and unbilled metered consumption (Muhammetoğlu & Muhammetoğlu 2017). This value is estimated by technical personnel familiar with the system. Metering inaccuracies value was estimated as 30% of the Authorized Consumption (AC) for 11 months before the replacement customer meter and 10% of the AC for two months after the replacement of customer meters in this study. Apparent losses resulting from meter inaccuracies are the main reason of apparent losses in well-managed water distribution systems (Arregui et al. 2018). A study showed that inaccuracies of water meters corresponded to 22% while apparent losses were calculated as 37% of system input volume (Mutikanga et al. 2011).

Water meter replacement campaigns, SCADA system operation and data analysis studies and physical leak detection activities are usually carried out by different departments in water utilities. Within the scope of this study, the studies carried out by different departments of the water utility were carried out in an integrated manner in the same period and the obtained data sets were analysed together. Thus, water losses, which were at the level of 52% in the pilot study area, were reduced to 35%. When the amount of water supplied to the system before and after the study are compared, the amount of water supplied to the system decreased by 11,058 m3/month and the authorized consumption increased by 7686 m3/month. Also, water losses in the PSA were reduced by 17%. In addition, the NRW level, which was 53% before the study, was reduced to 37%. Thus, the revenue of the water company increased by 16%.

The integrated water loss management actions mentioned in this study show us that the integration of different water departments in developing countries will reduce the levels of water losses and increase the revenues of the administration.

Pipe bursts in drinking water networks are mainly due to plastic and old pipes. Within the scope of this study, 62% of the failures in the PSA occurred in service pipes and polyethylene pipes. The findings of the study can be concluded as follows:

  • In addition to the decrease in the rate of water losses, the decrease in the amount of water supplied to the system and the increase in the amount of revenue water are important for water utilities.

  • Special attention should be paid to the pipe selection and storage criteria (standby in the sun, etc.) used in the drinking water network.

  • The study reveals the importance of ensuring integration between units in water utilities to carry out the required studies and to analyse the findings.

  • Due to the porous and permeable ground structure in karstic areas, not all the leaks in the drinking water network are visible on the surface. Therefore, physical leak detection studies should be carried out at regular intervals as it becomes difficult to detect the faults of water pipes, especially in karstic regions.

This research study was supported by the General Directorate of Antalya Water and Wastewater Administration (ASAT) of Antalya Metropolitan Municipality.

Data cannot be made publicly available; readers should contact the corresponding author for details.

The authors declare there is no conflict.

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