A positive-displacement pump for fluid products, in particular paints, colorants and the like, comprises a pump body (2) in which there is formed a pumping chamber (3), in which a piston (5) is mounted for sliding and is controlled so as to advance and withdraw in order to vary the useful volume of the pumping chamber (3). The pumping chamber (3) is placed in communication with a pumping pipe (38) leading into an upper region (42) which is located at the highest location of the pumping chamber (3).