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In a distribution system, a considerable amount of water gets wasted and lost either due to leakage or unauthorized water connections. These losses can amount to 15% of the total consumption even in a well-managed distribution system, and in case of faulty systems, the losses can be as high as 40%.
This wastage will directly increase the per-unit cost of pure water. Thus, for effective management of the system, it becomes essential to detect the points where water is being wasted. Proactive steps should be taken to rectify the faulty pipes and stop the wastage.
1. Methods to Detect Leakage in a Distribution System
The methods which can be adopted to detect the leakage of water through pipe joints, junctions, and water mains are as follows:
1.1 Direct Observation
This method mainly involves carrying out practical observations on wet spots on unpaved grounds, or the rise of spring at odd places, or luscious green growth at a specific spot. These types of leakages are easier to trace on clayey soils in comparison to sandy soils. However, the exact location of the preliminary indications has to be confirmed using sounding rods, waste detection meters, etc .
1.2 Using Sounding Rods
In this method, a sharp pointed metal rod is forced into the ground along the pipeline and then pulled up for inspection. Just by observing, one can identify the moist and muddy spot that indicates the presence of leakage. The sound of the leaking water can be heard clearly when one places their ear on top of the inserted rod, thus confirming the leakage point.
Another way to magnify the sound of leakage is by the use of an instrument called sonoscope or aquaphone. The sound of the leakage is amplified to a greater extent than the rod. To increase the effectiveness of the instruments, these experiments must be carried out at night when there is comparatively lesser noise.
1.3 Plotting the Hydraulic Gradient Line
In this method, the pressure at multiple points is measured along the suspected line and then the hydraulic gradient is plotted. In case there is a kink or fluctuation in the slope of the hydraulic gradient line, it will indicate the presence of leak in the pipeline. The graph will also help in detecting the location of the leakage.
1.4 Using Waste Detection Meter
Although the devices are named as ‘waste detection meters’, they do not actually measure the quantity of water that has been wasted. These meters measure any unusually high flow of water through a water main when the consumption of water is low i.e. in the nights or early mornings.
The unnaturally excess flow from a particular portion of the pipe depicts a leakage through that particular section, provided that there is no unusual high consumption in that specific vicinity.
First, the suspected locality is isolated and all the supplies, except the head of the chosen locality, are shut down. The waste detection meter is then fixed at the head of the main supply pipe and the water is allowed to flow to the locality after getting recorded by the meter. After this, the other laterals and branches in the locality are shut down progressively.
Thus, the flow recorded in the meter will drop down at each shut-off. If the shut-off indicates a disproportionately large drop in the listed flow, that shows that the pipe is leaking. The defect can then be corrected.
One of the widely used instruments is Deacon’s wastewater detection meter, which is very accurate and sensitive. When the water passes through such a meter, it forces down a brass disc which is otherwise balanced by a counterweight.
This movement of the disc is conveyed by a rod to a pencil point. The pencil then moves up and down vertically on a graph paper with respect to time. The meter is designed in such a way that it automatically records the quantity of water that flows through it.
The losses can amount to 15% of the total consumption even in a well-managed distribution system and in case of faulty systems, the losses can be as high as 40%
Leakage can be detected by observation, sounding rods, hydraulic gradient line, and by using waste detection meter.