It is very important to keep your water clean. Your feed water supply is a good place to start by installing a low pressure filter before the pressure washer. Quite often a filter on the inlet is not enough. A small piece of dirt picked up by a coupling on your high pressure hose, wand or other accessory can wreak havoc with your nozzle or mult-nozzles.
These are easy to install and clean. You can put them anywhere in the high pressure side but usually they are installed as close to the nozzle/s as possible