Abstract: A cleaning system for a printing press having a chamber for the cleaning liquid, a supply line with a valve for controlling the flow of liquid into the chamber and a nozzle connected to the chamber at a point above the bottom of the chamber and extending above the area to be cleaned. A siphon of inverted U-shape having an inlet extending to near the bottom of the chamber is positioned so that the outlet is below the inlet and above the area to be cleaned. The siphon is sufficiently shallow so that the siphon is completely filled when the cleaning liquid is being discharged through the nozzle, with the result that when the valve is closed the siphon serves both to lower promptly the level of liquid in the chamber and to cause a reverse flow of air through the nozzle, to inhibit dripping therefrom.