Part of the amount of water distributed through the water supply network is not recorded by the water meters of the consumers due to inaccuracies, false indications of water meters and other related causes, or even due to water losses. These losses are mainly due to leaks that cannot be detected in time or damages to the network caused by third parties. The percentage of non-revenue water was reduced to a satisfactory level before the imposition of water supply restrictive measures during the period 2008 - 2009. It should be noted, that in times of water restrictions, firm conclusions regarding levels of unaccounted-for water cannot be drawn because the network remains empty for long periods of time and the water pressure is lower than usual. Under such circumsances the continuous monitoring and location of non-registered leaks is impossible and thus the percentage of unaccounted - for water rises to disproportionately high levels, after the restoration of continuous water supply. After persistent and laborious efforts the percentage of unaccounted - for water is now maintained at very satisfactory levels since this is one of the main objectives of the Board, the success of which is in the utilization of the latest electroacoustic equipment detecting hidden leaks and in the replacement of stopped and old water meters, so that the recording of consumption is done with a higher accuracy.