With the thought in mind>>>>I don't know what I don't know. My understanding is the tip size, is fixed (indexed) to the psi & gpm. then regulating to wash whatever, with the unloader valve. and distance from object to achieve the end results. Hope that helps, lots of smarter people here than me.

from tip in distance on concrete use 4 to 6 inches on wood use from deck 12 inch from tip on sideing use 3 feet on dust on plants use 8 to 12 feet. you only need 2600 to 3000 psi pressure washer unless you pro cleaner are using 4000 psi remove paint from steel.

Leave the unloader alone, it is best left at the manufacturers operating pressure. Set too high, the unit will stall when the gun is closed, too low, the pump will cycle or 'hammer' when the gun is open. Most washers use either an adjustable tip or interchangeable nozzles.

Canguy, I'm sure your right about the unloader valve (best left alone) any ideas as to why many unloader's have a big convenient knob to adjust the pressure? TIA