Abstract: A water injection device for automatic de-scaling of steam irons comprises an axially displaceable injection plunger (21) which controls the communication between a reservoir (4) and a vaporization chamber (3) according to whether the flexible annular lip (17) of a nozzle (8) surrounds the plunger either in a smooth region (28) or in a laterally recessed region (26). A flexible skirt (19) surrounds the flow passage downstream of the lip (17). The injection plunger (21) terminates in an annular de-scaling boss (31) which is surrounded by the skirt (19) when the plunger is in the closed position.