Distribution system deficiencies continue to be responsible in many cases for waterborne disease outbreaks urban areas, a statistic that underscores the need for water suppliers to effectively control water quality within the distribution system. The drinking water companies are responsible for producing and supplying safe, high quality water for costumers. According to the legislation of Latvian government the drinking water quality should meet the standard at the customer tap, therefore the supplier is forced to analyze water quality not only at the outlet from the treatment plant but in the distribution network as well. Flushing is one of the most powerful tools available to a water utility for maintaining this control. Unidirectional flushing (UDF) is a refinement designed to bring water through the system in a controlled fashion at velocities sufficient to provide a scouring action within the distribution piping.