There is described a method and a system for cleaning an ink chamber (1) of a printing unit. The system includes a storage tank (10) which via a high-pressure pump (9) is connected with a hydrophore (2). In the hydrophore a high pressure is built up, and the hydrophore is connected with cleaning nozzles (40) via a valve (5). Thus it becomes possible to inject a shot of cleaning liquid into the chamber by switching the valves (5). The cleaning nozzles are preferably designed as a mushroom-shaped plug (40) with a stem (41) which is mounted in the chamber wall and which has a circular domed top (43) of elastic, resilient material. When injecting cleaning liquid, the elastic plug will spray cleaning liquid out into the chamber, and after shutting off the pressure, there will be a self-closing effect.