Abstract: An electrolytically activated, microcidal aqueous solution is disclosed which is used in the elimination and control of biofilm in dental unit water lines. The solution has a pH between 6.75 and 10 with microcidal as well as anti-oxidising, dispersing and surfactant properties, rendering the solution bio-compatible and non-corrosive, as well as capable of eliminating biofilm in dental unit water lines, while simultaneously dispersing and dislodging the biofilm from the water lines so as reduce the micro-organisms in the dental water to a predetermined level.