According to various embodiments, an IPP includes unbiased one-way check valve assemblies either independently or in conjunction with other valve assemblies to direct fluid into and evacuate fluid out of inflatable penile cylinders. The fluid transfer system transfers fluid from the fluid reservoir to inflatable penile cylinders and includes a fluid transfer bulb, unbiased inlet valve assembly, unbiased exhaust valve assembly and spool valve assembly. The cylinder deflate mechanism evacuates fluid from the penile cylinders to the reservoir and includes a deflate actuator, unbiased return valve assembly, and spool valve assembly.
