The heart of a high pressure cleaner is the nozzle, which shapes the water jet.  Even a slight change in the geometry of this seemingly inconspicuous component can have a big effect.  The so called power nozzle, for example, is shaped in such a way that it produces a sharp contoured, concentrated jet of large, coherent droplets, which removes dirt much faster than a normal nozzle, using less water and detergent in the process. The reason is the higher mechanical impact pressure achieved by this nozzle – it is about 40% higher than a conventional nozzle.

Basically, the impact pressure breaks up and loosens the layer of dirt, thus producing the desired cleaning effect.  The bigger, faster and more concentrated the impact of the water droplets on the surface, the better the cleaning result.  The factors involved in this process are nozzle pressure, water flow rate, geometry and spray angle of the jet.  The factors depend essentially on the shape and size of the nozzle orifice.  Narrowing the flow ports converts pressure into kinetic energy.  The force of impact decreases as the distance between the nozzle and object being cleaned increases; at a distance of 30 cm, it is only one hundredth of its initial value.  Depending on type of surface and degree of soiling, the spraying distance should be no greater than 10 to 30 cm.

There are three different jet patterns, i.e. fan, pencil and rotary jets. The fanjet achieves high area coverage:  Water emerges from the nozzle at a spray angle of up to 45° to create a broad jet.  This type of jet is also used for applying detergents and disinfectants.

The concentrated pencil jet, on the other hand, achieves a high impact pressure and very good mechanical dirt removal.  Therefore heavily soiled areas are best cleaned with pencil-jet nozzles.  The working width and area performance, however, are relatively small because of the narrow spray angle.

The so called rotary nozzle combines the cleaning power of a pencil jet with the higher area coverage of a fanjet.  The rotary nozzle's pencil jet, which rotates at high speed, and the linear movement of the spray lance produces a wide spray pattern that uniformly covers the surface to be cleaned.  The rotary nozzle achieves an area coverage, which is ten times greater than that of conventional pencil-jet nozzles and is therefore ideally suited for heavily soiled surfaces, which are insensitive to pressure.

A combination of several nozzle types is also possible.  There are triple nozzles, which allow the user to work alternatively with a fan or pencil jet without having to change the nozzle, and to add detergent in the low-pressure mode.