Precompression system for a liquid dispensing device and method of assembling such precompression system

The invention relates to a precompression system (7) for a liquid dispensing device (1), which prevents liquid from being discharged until a predetermined pressure has been built up. The precompression system (7) comprises a pump (3) for drawing liquid through an inlet (5) into a pumping chamber (15) and discharging it through an outlet (6) and a precompression valve (27) disposed between the pump (3) and the outlet. The precompression valve (27) allows liquid in the pump chamber (15) to reach the outlet (6) only after the predetermined pressure is established. The precompression valve (27) comprises an elastic diaphragm (32) normally closing the valve opening (30), a first side of said diaphragm (32A) facing the valve opening (30) and in fluid communication with the pump chamber (15), and a second side of said diaphragm (32B) in fluid communication with atmospheric pressure. The elastic diaphragm (32) may be prestressed in its normally closed state and further stressed in an open state. The invention further relates to a method of assembling such a precompression system in a liquid dispensing device.