A surface treatment machine, comprising a frame configured to translate with respect to a surface to treat, a surface treatment element connected to said frame and configured to treat with liquid a surface, a reservoir connected to the frame arranged to provide liquid to the surface treatment element through a delivery mouth; an adjustment element arranged to feed adjustably the liquid supplied from the reservoir to the delivery mouth. It is then provided a sensor configured to measure the flow-rate of the liquid from said reservoir towards the delivery mouth. A control unit receives from the sensor a signal proportional to the flow-rate for adjusting the adjustment element responsive to this value, in order to deliver the liquid with optimization of the flow-rate. It is possible then to maximize the range of the machine, and to optimize the working time of the operator.