A system for adjusting water in a domestic water diffuser, in particular for opening and closing water in a shower or bathroom or kitchen sink and for adjusting the flow rate, is described. The system comprises a shutter with at least one metal part slidable inside a cylindrical chamber with a diameter substantially equal to the diameter of the shutter; the system also comprises a pushbutton comprising a magnet; the pushbutton is configured to be operated by means of a finger to mechanically displace the shutter by means of the magnet along an axis of the cylindrical chamber, into two different positions, corresponding to opening of the flow or closing of the flow of water from a diffuser, the pushbutton being also rotatable about the axis, to vary the open position of the shutter along the axis and a corresponding flowrate.