Abstract: In a two-stage liquid injected helical screw gas compressor a bypass line with a check valve is provided between compressor stages for delivering compressed gas from the first stage directly to the compressed gas receiver and liquid reservoir. Bypass of gas to the reservoir at startup assures pressurization of the reservoir and early flow of liquid to the first and second stage compression chambers. As the working pressure in the second stage discharge line increases above first stage discharge pressure, the check valve closes and all flow from the first stage is conducted through the second stage compression chamber.