General Remarks

Water leakage measurement and its structuring are performed by implementing a „Water Balance“.  Water Balance system efficiency control program which is regularly being carried out in all water utilities in countries around Western Europe and USA is definitely accompanied by leakage detection program.   Water Balance can help a water utility reduce its water losses, revenue losses and achieve better usage of water resources.

Water Audit shall facilitate the identification of water losses and costs the utility has, and it shall also help check the accuracy of the document and system control equipment, having the selection of water loss reduction program as a main target.

In order to perform Water Balance of one water system it is necessary to:

1. Posses adequate maps which have to be verified and updated;
2. Test all water meters and flow meters at sources and in the water distribution system;
3. Posses verified and updated documentation on metered water inflow into the system (information on bills delivered) and unmetered water, including assessment of water consumption potentially not being metered (parks, public institutions and fire safety);
4. Test the accuracy of all (big) water meters and a certain number of small ones selected randomly;
5. Inspect all metering devices in the context of right size, installation and operation;
6. Site investigations of distribution and system operating procedures.

Zone loss metering represents one of the segments or the continuation of the Audit.

Flow loss metering and water consumption in all water systems except those smallest ones with less than 500 connections, is carried out by zones.  Loss metering DMAs are sections of the water system which at certain point can be isolated from the rest of the water system.  In case that is impossible, the DMA has to be organized in a way that water zone inflow could be measured in parallel to the zone outflow.  DMAs are being defined with the purpose of increasing metering accuracy and reducing its costs.

In order for the measurements to be as efficient as possible, it is highly important that the first DMA in which the measurements shall be carried out be properly selected.

This chapter shall describe and present the following:

1. Data collection mode and methods for efficient measurement and water loss detection,
2. Identification of resources and equipment necessary for zone water loss metering and sound leak detection,
3. Specific techniques for the identification of individual defect values, total losses and useful water consumption,
4. Analysis of data on detected leakages,
5. Data and information entry form during site

 Procedures for the Selection of the First “Pilot DMA”

While selecting the first zone where the loss measurements shall be performed, it is preferable to select a part of the network with high losses which shall soon be justified by the measurements and give incentives to the water utility to continue with measurements and water loss detection.

Water utilities having control flow meters installed in their network, by performing water flow control, can identify locations, i.e. parts of the network with significant losses.

Water utilities not having flow meters have experienced technical staff that usually has assumptions in reference to locations with highest loses which are in most cases correct.

The safest pilot zone selection method is to introduce network defect database.  Network defect database is a program in which all data on each defect incurring in the system is being entered (One of these Data Base is possible download here).

Database should be created in a way to give detailed reports on all types of defects, as well as reports on locations with defects recurring several times.  Locations where defects recurred the most should be selected as a firs pilot zone.

For this criterion of pilot zone establishment basic assumption is that the losses in the network are dominant, and not water wastage at customers’ installations. 

In order to select a pilot zone it is necessary to comply with the following conditions.

1. Existence of GIS (with accurate data) or 1:500 or 1:1000 zoneThe map has to be updated with all objects, pipes, valves and connections drawn.  This is usually the first and most common problem with pilot zone establishment, and very often the decisive factor during for selection.  
2.  DMA should have between 500 and 3000, depending on the dominant customer
3. DMA can be an industrial complex or a clinic center, and in such an event the number of connections could be a lot smaller.
4. For the establishment of a pilot DMA  it is necessary to have only one water inflow 
5. A “main manhole” should be constructed at the water inflow point, if not already existing, and a measurement device should be placed inThe manhole should be dry and big enough to freely place the measurement device in it.
6. The manhole has to be secured in order for the measurement device not to get stolen.
7. In order to reach a full isolation of the DMA operating border, section and house connection valves have to be installed at all zone outflow 
8. All customer water meters within the DMA have to be operating and calibrated in dueWater meter data is usually stored in the Financial Department in the form of a water meter “ID card “ or in a financial program. This data refers to all the customers within the water system and it is most often the case that only data on customers in the pilot DMA cannot be extracted.  In rare cases and in the event it is possible to do so, a question arises about the mode in which the Technical Department shall manage the accuracy of water meter in the future.  Due to all these reasons the best solution is to create a simple database for the needs of the Technical Dept. thanks to which the responsible persons from the Technical Dept. could, at any moment (both before and after the measurements) be familiar with the locations and number of inaccurate water meter that need calibration.  Within this database a part referring to the number of water meters the utilities have on stock can be integrated.  Relevant and updated data on all customers in the pilot zone have to exist.  This data has to be collected directly on site since there is a possibility that data in the computer, if existing, is incorrect.
9. Each next DMA should follow the previous one so that they all together could comprise a whole which could be

Procedures for DMA Loss Measurement Preparations

For the implementation of measurement program in the DMA selected in the water system it is necessary to plan and execute the following activities:

1. Nomination of staff and allocation of responsibilities and obligations,
2. Identification of measurement and leakage detection equipment,
3. Customer and water meter data collection on site,
4. Technical data collection on site on the operation of valves and other objects within the subject zone important for the production of the plan and performance of measurement,
5. Detection of visible defects in the zone,
6. Determination and numeration of measurement points within the zone,
7. Control isolation of the zone from other parts of the water system,
8. Loss measurements using Balance Method,
9. Loss measurements using Night Measurement method
10. Defect detection by sounding,
11. Defect repair by sounding,
12. Control measurement of losses with the purpose of identifying values of reduced losses.

The first seven items are being transferred in a Loss Measurement and Detection Plan which is being prepared prior to the beginning of the loss measurement campaign.

Plan is given to each member of the team so that he can get familiarized with all the requirements of the planned campaign.

Nomination of Staff and Allocation of Responsibilities and Obligations

Leakage detection and measurement is a very expensive and responsible job. For its implementation it is necessary to nominate staff and perform allocation of tasks and responsibilities.

While planning the number of staff participating in the measurement campaign it should be taken care of the following:

1. Determine the number of workers who shall be installing theIt is usually the case that 2 employees experienced in installation and programming of certain equipment are sufficient.  Two workers can install 3 portable flow meters, three pressure meters and program them in less than two hours provided that all measurement points have been properly prepared.
2. During night measurement, if the device is located in the open space, nominate employees who shall monitor the equipment during theThese persons shall occasionally record data from the device in the form (attached).  Records are always made due to security reasons regardless of the fact whether the device has data logger or not.  The recording interval is being predetermined (determined time interval, opening or closure of valves and alike).  For each device in the open air at least one person should be allocated.  Once the personnel installing the equipment have finalized their job, they could join this team.
3. Determine the number of employees working on valve opening and It is usually the case that 2 employees (reliable once due to the fact that the accuracy of all data obtained by measurement depends on them) are sufficient for this operation.  All operations are executed upon the request of the team leader.
4. For meter reading (by applying the Balance Method) a sufficient number of personnel has to be allocated so that the reading of all water meters could be performed in one Based on the norms, one person can read between 70 (in rural area) and 100 water meters (in urban areas) in a day.
5. The number of nominated personnel dealing with leakage detection is always even and all activities are being executed in. For network inspection (identification of defect macro locations by the sounding of water meters, hydrants, valves etc.) one pair can examine 2.5 km of familiar network.  The time necessary for the precise location of defect cannot be defined since it depends on a lot of subjective and objective circumstances (type of pipe, pipe depth, pressure, type of soil, surrounding pipelines, traffic, sea waves etc).  

    Identification of Measurement and Leakage Detection Equipment

Equipment in the possession of the water utility represents a limiting factor during the implementation of measurement.  Each measurement and leakage detection team possesses or disposes of the following basic equipment:

1. Portable ultrasonic flow meter,
2. Pressure probe with data logger,
3. Correlator,
4. Aquaphone (Geophone),
5. Metal pipe locator,
6. Non-metal pipe locator.

The equipment has to be regularly maintained and serviced.

In addition to the abovementioned equipment it is also necessary to possess additional equipment:  length measurement wheel, ultrasonic device for wall thickness measurement, pressure gauge and GPS device.   

It is necessary that the team be equipped during work with tools and devices such as: water pump, fuel engine, wrenches for opening the valves, tools for lifting manhole lids and alike.

Customer and Water Meter Data Collection on Site

Prior to the beginning of measurements in the pilot DMA, water utility staff goes on site and collects data essential for proper loss measurement.

In that context it is necessary to draft a universal form for each customer (form sample is attached), onto which the following data shall be recorded:

1. Name and last name of the person collecting data (ViKs employee),
2. Name and last name of the customer,
3. No. of household members,
4. Water meter profile,
5. Water meter manufacturer,
6. Water meter serial number,
7. Water meter address location,
8. Date when the water meter was last calibrated, (written on the seal),
9. Consumption index on the water meter (m³),
10. Exact date and time of reading.

Greatest problem during this data collection occur while reading water meter calibration date from the seal.  In order to do this, make an improvised telescope by installing a magnifying glass into the “printer” paper carton roll.   

It is of special importance to emphasize to the customers that these data are being collected for the water loss measurement purposes and for the purpose of better water supply, and that they have no reason to report fewer number of household members.

All data collected are entered into the database for further processing.

Customer data is being divided into four groups:

1. Small residential objects – private houses,
2. Apartment building (more apartments on one water meter),
3. Small businesses,
4. Public institutions and industry

Each of these categories consumes water in a different way in the context of flows and consumption distribution. 

 Technical data collection on site on the operation of valves and other objects within the subject DMA important for the production of the plan and performance of measurement

Technical data based on which measurement plan is made are collected on site. It is necessary to collect the following data:

1. Pipeline data (material, age, profile, connection mode, break history, nominal pressure)
2. Data on points suitable for the installation of measurement equipment – take coordinates and take twoThe first photo is taken in order for the wider area around the measurement point to be visible.  The second photo is shows the measurement point from close range. Geographical coordinate is taken with GPS device,
3. Valve data – location, diameter, type, closure mode andTake a photograph of each valve with digital camera,
4. Data on flow meters and water meters – type, diameter, age, installation mode, reading mode, reading frequency, break history,
5. Data on hydrants – location and unmetered consumption,
6. Reducing valve – location, inflow and outflow pressure,
7. Check valves – location,
8. Air valves – location,
9. Booster stations – location, operation frequency, maintenance mode, access,
10. Sounding disturbances than could be expected in the selected zone,
11. Data of traffic impact on the measurement campaign and leakage detection by sounding,
12. Data on most convenient time of day or night for the execution of leakage detection sounding,
13. Data on most convenient time of day or night for the executionprecise defect detection (some teams for leakage detection execute this activity few days after the control detection by sounding campaign or even at the end of the week),

Measurement points and valves are being numerated by using recognizable signs.  All coordinates are being transferred into the GIS.  Valve and measurement point coordinates can also be entered into the Google Earth program and by using that same program introduce the staff included into the measurement campaign to the measurement plan. 

Google Earth gives a much clearer picture of the zone to those who do not have experience in map reading, or in case the maps are not updated. 

Detection of visible leaks in the zone

By visiting site and collecting information from locals locate preferably all visible defects and immediately initiate their repair. It is essential to do so due to at least two reasons:

1. Sound volume is transferred onto the pipeline with visible breaks and can override the sound volume created by underground breaks,
2. Create a bad image about the water utility with the customers which can have impact on collection reduction.

In the same manner, try to detect as many hidden defects.

Water utility must be ready to momentarily initiate the repair of each hidden defect which does not get detected during this phase but during sounding activity. 

                  Determination and numeration of measurement points within the zone 

Based on data collected, during the next phase it is necessary to locate all measurement point in the DMA.  At the DMA inflow point, a position of the measurement point is being defined, as well as positions of all auxiliary measurement points within the DMA.  All measurement points are being numerated.

While determining the location of the measurement point, a device which is going to be installed on it should also be determined.

During the selection of the measurement location, the following should be taken into consideration: 

1. Location at which the manhole shall be constructed must be dry, and the manhole itself has to be large enough to easily accept the installation of measurementDuring the construction of the manhole for temporary measurements, one should bear in mind that there is enough space for the fixed meter to be installed, if later on should the need arise.
2. If possible, the manhole should be located in the vicinity of electric and telephone lines in order for the device to get easily supplied with electricity and in order to potentially perform electronic remote data transfer from the meter into the PC where the data would be
3. It is of special importance that the measurement location be protected from potential vandalism of this refers only to mobile meters which are very expensive and easy to uninstall; and even though there is a handful of people who know how to use them, when the device is left unsecured, especially in deserted places, it is quite probable that there would be someone who would steel it.  Water utilities apply different methods to secure their measurement points.  The safest way to secure the manholes is to provide physical protection, and since it is referred to the measurement on the sources which also have to be physically protected, than it is most often the case that it is easy and simple to execute.  When measurements are performed outside the source itself, the question remains whether it is good to install a padlock on the manhole or not.  Both alternatives have their pros and cons, because if the manhole is not locked, the device can be stolen easily and swiftly.  If the manhole is locked, the padlock itself, which is visible, makes clear that there is something valuable in the manhole.  An original way of some water utilities to secure their mobile measurement devices is to park a car over the manhole cover and in that manner prevent potential device theft.  Measurement device security should be taken into consideration during the construction of the manhole already.  Manhole construction should be such that it does not display the measurement device the same moment the cover is lifted.
4. Manhole location must be downstream from potential water overflows or unmetered
5. If there is an opportunity for further development of the settlements of the extension of distribution network itself, then the manhole construction point must be upstream from respective settlement.
6. Considering the fact that electromagnetic and ultrasonic meters, or Wooltman’s meters are being used for source measurements, a shared characteristic of them all is that they can only meter correctly if the pipe profile is fully filled with a very important precondition for the selection of measurement location is that the pipe is filled with water.  One should also take care not to leave any possibility of creating air pocket at the measurement point.
7. Pipe where the flow meter shall be installed, being it a fixed or mobile version, must be on a certain line at a certain length upstream and downstream from the measurement device in order to avoid uneven turbulence at the measurement point due to which the measurement would be incorrect. 

Control Isolation

Prior to initiating the flow monitoring, a DMA is being isolated by closing the zone’s gate valves.  A flow meter and a pressure meter are being installed in the main manhole at the regulated distance downstream from the valve in the main manhole. 

DMA “isolation” testing is being carried out by closing the upstream valve in the main manhole. If the pressure abruptly decreases to zero, the DMA is “isolated”.  If that does not happen, then it means that the zone is “not isolated” and that the measurements cannot be performed before all causes of non-isolation are removed.

If due to some reasons it is impossible to install the metering device downstream from the valve, or if there is no pressure meter, the only way to test the isolation of the zone is to close the valve and check whether the customers at that same moment have water supply.   

Loss Measurements Using Balance Method

Balance Method is required in order to make difference between the average daily water volume supplied to the pilot zone and average daily sum of all water volume read from customer water meters.

The result of this difference represents an average daily volume of losses in the pilot DMA 

Total water losses represent the sum of:

1. Defect in main pipelines,
2. Defects in the distribution network,
3. Inaccuracy of low flow metering at customer water meters
4. Water volume consumed at illegal connections,
5. Measurement mistakes.

Balance Method is being applied in two stages, and due to eliminating daily fluctuations in consumption, the measurements last for seven or fourteen days.  If the zone is an industrial complex or alike and consumes water in the same manner every day, the measurement can last shorter.  

1. While the flow meter installed in the main manhole at water inflow point into the pilot DMA continuously measures flow, the reading of all water meters in the zone is being performed and the time of the readingThe reading should be done swiftly, in one day, if possible.  Average norm of the meter reader is 100 water meters per working day in urban areas, and 70 water meters per working day in rural areas (working day being 8 hours).  Based on this norm, an assessment of the number of people required for meter reading in one pilot DMA is being made.
2. All meter readings are being entered into the loss calculation model.
3. The second stage is being carried out in the same way as the first one, but at least seven days after the first Seven day time period is required because the customers do not consume same quantities of water each day of the week.
4. Data is resaved in the computer.
5. Water loss calculation comes down to the calculation of each customer’s average daily water consumption read at customer’s water meter in m^3. While performing this calculation it must be taken care of the time of reading.  The sum of all customers’ average daily consumptions is being deducted from the average daily water inflow in the DMA.
6. If in the manhole there is only a water meter, then the average daily water inflow into the DMA is being calculated in the same manner as with the customers’ waterIf the data logger is installed on the water meter, or if the flow meter is being used, figure on average daily water volume is obtained directly from the device.   

Loss measurements Using Night Measurement Method

Generally, it is considered that during the night there are moments with no consumption which furthermore means that the volume of water metered during late night and early morning hours represent water losses in the network and water wastage at customer’s installations.  True enough, there are customers who consume water also during the night such as fountains, firefighters or industrial night shifts.  These customers must be located prior to the beginning of measurements and their average daily (or night) water consumption.

All valves in the DMA must be operational!!!

A correct way to measure water losses by applying night measurement method entails prior finalization measurement according to the Balance Method.  From the result of Balance Method it can be seen what time of the night is the time with minimum water consumption, since night measurements are carried out only and exclusively during times when the water consumption  is the lowest.  That time is usually between 00:00am and 05:00am.  

By performing night measurements the amount of water wastage for each customer category can be determined, and in case there are customers with enormously high losses, then their wastage calculations should be done separately.

Figure: Typical daily curve of water distribution