A pumping apparatus is provided, which comprises a piston (1) for reciprocation in a pump working chamber (3), a valve, coupled to said pump working chamber (3) in order to permit liquid flow only unidirectional and a drive unit for reciprocating said piston (1). The liquid in said pump working chamber (3) is compressed to a high pressure, at which compressibility of the liquid becomes noticeable. The piston (1) is at least partially coated with a diamond-like carbon coating (2), adapted to provide a reduced abrasion of said piston (1).