Operation of the Water Leakage Control System

The basic principle of "Water Leakage Control System is the continuous monitoring of the "Leakage Control Zone's Minimum Night Flow".

 

The Chania water network has been divided into thirty "Leakage Control Zones" for water leakage monitoring and control. A "Leakage Control Zone" is an area, of the water network, isolated from its adjacent, by closing all the water valves, located peripheral of this area, except those, where flow meters have been installed to count the inlet and the outlet water flow from this area to the adjacent one. D.E.Y.A.X. has completed the installation of the "Leakage Control Zones" at the following three stages: planning each leakage control zone, checking each leakage control zone, installing the necessary electromechanical equipments.

"Planning each leakage control zone" has to do with the way that a zone is supplied with water, the number of consumer's flow meters and the number of water inlet and outlet points of a leakage control zone.

 "Checking each leakage control zone" has to do with the final "installation of control leakage zones". For carrying this out, all the peripheral valves of each leakage control zone, have been checked to isolate this zone from its adjacent. This happens only if the leakage control zones do not cause any pressure loss problems to the water network. Results of most checking are digging up, repairing, or replacement works for the water valves. A few interventions to the water pipe network and a few changes to the final planning of leakage control zone borders may occur.

"The installation of the necessary electromechanical equipments" has been carried out at appropriate locations inside the town of Chania, at the water inlet and outlet points of the adjacent leakage control zones. As a result of this, seventeen "Leakage Control Stations" (TSD) with the relevant manholes, flow meters and the electrical control boards, with the equipments for the monitoring of the water flow and water pressure, have been built. In addition the "Leakage Control Stations" have the ability to monitor the residual chlorine measurements of the water. Also, ten "Water Control Stations" have been built at several locations of the water network (e.g. pump stations, water tanks and water network junctions) with the relevant flow meters and the electrical control boards, with the equipments for monitoring of water flow, water pressure, water tank's level, residual chlorine and other data.

Remote controlled pressure reduction valves have been installed, on the water network in some leakage control manholes, to reduce the high pressures that appear inside a leakage control zone during the night. The result of this is the reduction of leakage and the protection of water pipe network from braking.

The above mentioned data, the relevant with the leakage control, collected, processed, monitored and stored by the SCADA (Supervisory Control and Data Acquisition) System of the Central Control Station computers, which is located at a building next to the Agios Yiannis water tank.

The following two techniques used by the water network repair party to search a leakage are:

The "Acoustic Detection", where trained technicians, using the sense of hearing and special equipments, try to pick up the sound that a water pipe network produces, during a water leakage. During a water leakage, through a small water network crack, a vibration of a changeable frequency is produced. This vibration is called "leakage noise" and can be picked up using special equipments. This leakage search technique is the main and most significant method for searching an invisible water leakage.

The "Cross Correlation Noise Detector" (a special electronic equipment) follows the same basic principle with the "Acoustic Detection", but this technique has the advantage that any noise coming from any extraneous influence (e,g. vehicles) is filtered and rejected. Also this technique lets us check, for any leakage, longer parts of the water pipe network in less time. This leakage search technique is also a very important method for searching an invisible water leakage.