There isn't a nozzle of any sorts with this so the water just dribbles out. I don't see the advantage of this versus an inexpensive brush and wand connected to your garden hose. I haven't tried connecting it to my extendable wand yet but if it does then the added reach of the wand might make this item worthwhile.
Cons:No real usable value
Carl Does Not Recommend This Product
You should still be getting the 2000 PSI water from your pressure washer pump through the brush. (Pressure washer PSI is measured at the pump, not the nozzle...)
With respect, please make sure you have your pressure washer turned on after you attach the brush, and the brush is firmly seated in the quick connector. If you still aren't seeing high pressure water through the brush you may want to check to see if there's a piece of the plastic molding blocking the water flow- I would try moving a slim dowel or other object down the shaft of the brush to make sure it's clear.
The water brush fits onto your pressure washer or your garden hose and is NOT a high pressure accessory. So it is working exactly as it should be. The PSI is measured when a nozzle is connected to your lance, not at the pump. GPM is measured at the pump.