Have you ever used a zero degree nozzle to clean a large space? If so you know what an incredible clean spot you get where the nozzle impacts the surface. You also know what a tiny area you get clean and how difficult it is to avoid streaking.
Enter the Rotary Nozzle. Simply put, the rotary nozzle is nothing more than a zero degree nozzle, except it spins at a very high rate of speed. If you hold a rotary nozzle in one place you will draw a clean circle in the dirt. Move it really fast and you will have a clean spiral. Move it at just the right speed and you have an incredibly effective cleaning tool.
There are many different types of rotating nozzles. Some have ceramic wear surfaces, some have adjustable diameter and other have springs to hold the ceramic parts together. All will eventually need maintenance due to the wear of the moving parts and the cleanliness of your wash water.
Prices vary a lot. The reason being is the construction. Cheaper rotary nozzles are made from plastic and steel parts. More expensive units are made from brass and ceramic wear parts. These expensive types usually have replacement wear parts available. Some of the cheaper models are throw away when they wear out.
The average homeowner will get a few years use from a cheap nozzle. The contractor should not even consider the cheap unit.
One way to increase the longevity of your rotary nozzle with ceramic wear parts is to ensure you pull the trigger on your gun when the tip is pointed down, not up. Ceramics are very hard (good wear) but brittle. With the tip pointed up the ceramic pieces have a small space between the fixed part and rotating part. When you pull the trigger the rotating part will slam against the fixed part, causing it to crack or chip. When pointed down these two pieces are together.
Another thing anyone can do is install a high pressure filter on the incoming port. Because two surfaces of a rotating nozzle rub together, constantly at very high speed, any small amount of dirt or silt in the water can cause excessive wear.