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Real Losses classifications PDF Print E-mail
Written by Administrator   
Tuesday, 04 September 2012 23:00

Real Losses (often referred as physical losses), represent the amount of water that leaks out in a given time through all kinds of cracks, holes and overflow. Classification of these types of losses  performed according to the position of origin within the Water supply  system and the size and leak duration.

  Classification based on place of origin and time of duration

There are generally three positions occurrence of real losses based on place of origin as follows:

  • Leakage from the transmission and distribution mains may occur at pipes bursts due to extraneous causes or corrosion, joints due disconnection, damaged gaskets and valves due operational or maintenance failure and usually have medium to high flow rates and short time of duration.

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  • Leakage from service connections up to the point of the customer meter. service connections are sometimes referred to as the weak points of water supply networks, because their joints and fittings exhibit high failure rates. Leaks on service connections are difficult to detect due to their comparatively low flow rates and thus often have long time of duration.
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  • Leakage and overflows from storage tanks are caused by deficient or damaged level controls. In addition, leakage may occur from masonry or concrete walls that are not watertight. Water losses from tanks are often underestimated, they have long time of duration, and though easy to detect, repair is usually very expensive.

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Classification based on leak size 

According to this classification leaks classified into three types:

  • Visible (Reported)  leaks primarily come from sudden bursts or ruptures of joints in big mains or distribution pipes. Leaking water will appear at the surface quickly depending on water pressure, leak size as well as on soil and surface characteristics. Special equipment is not required to locate the leak.
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  • Underground (Unreported) leaks, these faults have a flow rate greater than 0.07 l / s with pressure of 5 bar.  The presence of these leaks can be identified during DMA's measurements  and for their detection must use special equipment.
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  • Background leaks occur at joints and tubes. This kind of leaks have flow rate less than 0.07 l / s at a pressure of 5 bar. These defects can not be detected using leak detection  equipment,  their duration is very long, and can be eliminated only when carrying out pipeline reconstruction .
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While apparent losses can be nearly totally eliminated, a certain level of real losses will  always remain in any water supply system. This amount is known as Unavoidable Annual Real Losses (UARL). The difference between Current Annual Real Losses (CARL) and Unavoidable Annual Real Losses is considered as the potentially recoverable real losses. 

Real losses must be valued at the cost of producing water or at the purchase price, if water is imported.

In developed countries, real losses usually represent the most important component of water losses. However, in developing and emerging countries losses due to illegal connections, metering and accounting errors may often be of major significance to water utilities.