According to the invention, a steam generator is provided with a housing for forming a steam generating chamber, the housing having a steam outlet port. A heater plate is supported by the housing within the steam generating chamber. A water inlet valve is fluidly connected to the housing for selectively supplying water into the steam generating chamber whereby water is directed to the heater plate for conversion to steam. The heater plate forms a bottom wall of the steam generating chamber and is arranged to have a high point. The water inlet valve is opened and closed in accord with a duty cycle which alternates between two phases: a fill phase duty cycle and a steady state duty cycle.