Method for washing and separating pieces of plastics material from contaminating material that also includes metal elements, comprising the steps of: a. Supplying to a single washing chamber defined by a single washing container, through an inlet port, a washing fluid, having a first specific weight value (γ1), and the pieces of plastics material with the contaminating material; b. driving, in said washing container, stirring means provided with blades for generating in the washing fluid a turbulent stirring action to remove from the plastics material, through mechanical action, the part of contaminating material adhering thereto, wherein there is provided c. setting the tilt of said blades and adjusting the rotation speed (V R) of said stirring means to generate a thrusting action (F T) upwards so as to maintain in a floating condition the plastics material having a second specific weight value that is greater than said first value (γ1) of said fluid, and wherein there is provided d. limiting the force of said thrusting action (F T) to a value that is such as not to hinder the downward precipitation of said contaminating metal elements that have a further specific weight value (γ3) greater than said second value, and e. driving rotatable control means, arranged in a discharge channel diametrically opposite said inlet port and protruding transversely outwards from a lateral wall of said washing container, for retaining said plastics material inside said washing container for a time that is such as to obtain a desired degree of purity and decontamination for said plastics material, preventing the plastics material, once it has been supplied to the washing container, from exiting immediately without first undergoing the washing process through mechanical stirring, said discharge channel being bounded laterally by two side walls and below by a ramp wall that protrudes from a first height from the side wall of the container, extending in a tilted manner upwards as far as a second higher height, said rotatable control means extending between the two side walls and being positioned above said ramp wall, f. evacuating through controlled overflow, through an outlet port bounded by said discharge channel of said washing container, an outward flow (F out) of washing fluid and a quantity of already decontaminated plastics material (P'), wherein said already washed and decontaminated plastics material (P') is conveyed to said outlet port in a controlled manner through the action of said rotatable control means, and g. periodically evacuating, from a bottom of said washing container, the heavy contaminating material - including metal elements - which accumulates on said bottom during washing of the plastics material. a. Supplying to a single washing chamber defined by a single washing container, through an inlet port, a washing fluid, having a first specific weight value (γ1), and the pieces of plastics material with the contaminating material; b. driving, in said washing container, stirring means provided with blades for generating in the washing fluid a turbulent stirring action to remove from the plastics material, through mechanical action, the part of contaminating material adhering thereto, wherein there is provided c. setting the tilt of said blades and adjusting the rotation speed (V R) of said stirring means to generate a thrusting action (F T) upwards so as to maintain in a floating condition the plastics material having a second specific weight value that is greater than said first value (γ1) of said fluid, and wherein there is provided d. limiting the force of said thrusting action (F T) to a value that is such as not to hinder the downward precipitation of said contaminating metal elements that have a further specific weight value (γ3) greater than said second value, and e. driving rotatable control means, arranged in a discharge channel diametrically opposite said inlet port and protruding transversely outwards from a lateral wall of said washing container, for retaining said plastics material inside said washing container for a time that is such as to obtain a desired degree of purity and decontamination for said plastics material, preventing the plastics material, once it has been supplied to the washing container, from exiting immediately without first undergoing the washing process through mechanical stirring, said discharge channel being bounded laterally by two side walls and below by a ramp wall that protrudes from a first height from the side wall of the container, extending in a tilted manner upwards as far as a second higher height, said rotatable control means extending between the two side walls and being positioned above said ramp wall, f. evacuating through controlled overflow, through an outlet port bounded by said discharge channel of said washing container, an outward flow (F out) of washing fluid and a quantity of already decontaminated plastics material (P'), wherein said already washed and decontaminated plastics material (P') is conveyed to said outlet port in a controlled manner through the action of said rotatable control means, and g. periodically evacuating, from a bottom of said washing container, the heavy contaminating material - including metal elements - which accumulates on said bottom during washing of the plastics material.