This is one of the most important, yet trouble-prone protective devices on your pressure washer. It is used to relieve the water pressure within the pump whenever spray flow is blocked. The unloader lets the engine (or motor) keep running, though the operator may have let go of the trigger and stopped washing. The built-up pressure is diverted by the unloader, which "unloads" the pressure by taking the water from the exit area of the pump, channeling it back to the inlet area. The unloader also returns the flow of water to the gun when the operator is ready to clean again.