Abstract: A device for controlling and monitoring the level of a washing liquid in a washing unit of a printing machine which includes a wash tank having a washing liquid therein and a pickup roller mounted in the tank and rotatable in the washing liquid to lift the liquid on the surface of the roller and transfer it to a rubber blanket roller to be cleaned, comprises a control tank which is connected to the wash tank and arranged at substantially the same level as the control tank. A supply tank for the washing liquid is located above the control tank and supplies liquid into the control tank under the regulation of an electromagnetically controlled valve. The valve is switched in order to provide for flow from the supply tank into the control tank in accordance with the level in the control tank. The level of the control tank therefore maintains a level in the wash tank by virtue of the flow between the control tank to the wash tank.