Abstract: The fluid jetting device for cleaning surfaces comprises a housing having a fluid inlet for pressurized fluid and a first pressurized fluid space connected with at least one movable high pressure nozzle residing in the housing. A high pressure seal is formed between the nozzle and the housing. At least one mechanical separating means is provided in the housing to form a second pressurized fluid space containing another pressurized fluid, advantageously oil, adjacent the high pressure seal. The second pressurized fluid space is separated from the first pressurized fluid space by mechanical separating means to prevent dirt from reaching the second pressurized fluid space and the high pressure seal but the mechanical separating means allows transmission of fluid pressure in the first fluid space to the other fluid to allow pressure balancing. The sliding surfaces on adjoining sliding members at the high pressure seal may be made of ceramic material to increase life and reduce friction and wear.