A nozzle for spraying a pressurized liquid. The nozzle is adapted for processing a pressurized liquid through an orifice of the nozzle, where the pressurized liquid forces a nozzle member away from a seat. The nozzle member is moved by the pressurized liquid against a counterforce produced by a gas pressure. Gas pressure operates against a plunger to produce a force acting on the nozzle member in opposition to the liquid pressure. A desired upstream pressure of the pressurized liquid is established when the forces across the movable nozzle member are balanced. A desired upstream pressure of the pressurized liquid can be changed by changing the pressure of the gas that forces the plunger against the movable nozzle member.