Simplified multicolor fluid system for continuous ink jet printer

An improved construction for a continuous ink jet printing system of the kind having a chamber for receiving a plurality of ink cartridges, a plurality of ink supply sub-systems for delivering ink from the cartridges to respective print heads and a plurality of ink return sub-systems for returning ink from the print heads to respective cartridges. The cartridge chamber is constructed to be substantially air-tight and the ink cartridges have a vent opening to their interior. The chamber itself is coupled to a vacuum source and the cartridges in the chamber are maintained at the chamber pressure via their vent openings. The chamber evacuating source includes a source of compressed air and a venturi devcie coupled to the housing interior and the compressed air source. The compressed air source also can be coupled, via check valves structure, to provide drying air to the print heads.