Abstract: A pneumatic device for detecting continuously the hydrometric level of a water column, said device comprising a tubular probe dipped into the liquid column by a height greater than the distance between the two maximum and minimum levels set forth previously, a pair of pneumatic detectors of the minimum and the maximum level which are operatively associated to said probe and are put in action by changes in the air pressure occurring inside the probe itself as a function of changes in the column level, a gauge or indicator associated to the maximum level detector for signaling continuously the position of the water level, and means for starting or for stopping a motor-driven pump in correspondance to said maximum and minimum values.