Hi, Don't know the minimum PSI but my Blazer would only deliver a maximum of 1000psi. and that seemed to do a pretty good job.It needs to be somewhere in that region for the water pressure to spin the rotary spray bar and provide sufficient pressure to the floor. Don't forget as there are two nozzles the pressure is halved. Any lower psi and the spray bar would rotate more slowly, giving you a pattern of rings if you moved the wand too quickly.