In order to enable using water as a hydraulic liquid in a high-pressure piston pump for hydraulic circuits with nominal pressure more than 50 bar and up to at least 250 bar, on the one hand an area on the internal wall (10) of a cylindrical operating chamber (1), which cooperates with the external surface (20) of a piston (2) and is at least temporarily in contact therewith, consists of polyether-ether-ketone (PEEK), and on the other hand at least an area of the external surface (20) of said piston (20), which cooperates with said internal surface (10) of the operating chamber (1), consists of martensitic stainless steel. An eccentric (22) of a crank (21), which generates oscillating movement of the piston (2) along said cylindrical operating chamber (1), is offset relative to the longitudinal axis (100) of said operating chamber (1) at a predetermined distance (e) transversally with respect to said longitudinal axis (100), by which the crank (2) is at least during the most critical stage of the piston (2) stroke positioned at least approximately on said central axis (100) of the operating chamber (1).