First, remember that there is 120v or 220v that is easily touched. What brand pressure switch is it? If it is Square D, then the larger nut raises and lowers both the cut-in and cut-off at the same time. The smaller nut increases or decreases the gap between the cut-in and cut-out. Loosening the spring on the larger nut (counterclockwise) should lower the pressure. I would avoid the smaller nut unless you want to change the gap. If the smaller nut is too loose, the pump will never turn off because the cut-in and cut-off are too close together.