The invention refers to an apparatus for distribution and dispersion of water, saturated with air under high pressure, which apparatus is preferably intended for use in a flotation basin (1) in a water treatment plant in which it is positioned at the inlet openings (2) for the water to be treated in the flotation basin (1). The apparatus comprises a predispersion unit (27, 28) arranged in a distribution tube (22) or its connection piece (24) comprising a perforated tube arranged preferably co-axially in the respective tube through the perforations or reducing holes (26) of which the air saturated water during a first decrease of the pressure and corresponding dispersion passes on its way to the distribution tube (22) from which the water during a second decrease of the pressure and dispersion is pressed out into the flotation basin (1) through one or several openings (23) in the wall of the distribution tube (22).