How do you adjust water pressure through a pressure washer?

There is a couple of different options. Some washers are equipped with pressure adjustment knobs. Failing that...all come with either multiple spray nozzles or twist type vari-nozzles. For multiple colored nozzles, the use of various widening angle-of-spray nozzles gives a range of impact force. The wider the nozzle angle, the lower the impact pressure on the substrate. Vari-nozzles do the same thing by twisting the housing. Most washers do have a pressure setting control. Look for a spring loaded assembly. Turning back the force exerted by the spring will lower your pressure setting. It is most commonly preferred to lessen the impact pressure by widening the impact area of the spray rather than lowering the pressure directly as it offers better productivity. Of course, pulling back the nozzle a few extra inches from the substrate surface can lower the pressure also.