Abstract: A flooded compressor system has a compressor unit (10) with intermeshing rotors and a separator (12) for retaining a volume of liquid. The separator (12) is arranged to receive compressed gas and liquid discharged from the compressor unit (10) through an outlet (17) and is formed solely by a single length of pipe of substantially uniform cross section which has a first substantially horizontal portion (19) to retain a liquid pool (18) and a second elevated portion (23) connected to the first portion by a bend in the pipe. A compressed gas outlet (25) leads from the second elevated portion to a separate filter element (14), and a liquid filter element (30) is mounted from, and communicates directly with the first horizontal portion of the pipe.