Multi-stage displacement pump

A multi-stage pump, comprising:

• a first pump stage having a first chamber having a first chamber diameter and a first chamber volume, the first pump stage further comprising a first inlet channel and a first outlet channel each in fluid communication with the first chamber;
• a second pump stage having a second chamber having a second chamber diameter and a second chamber volume, the first and second chambers being coaxial, the first chamber diameter and the first chamber volume being greater than the second chamber diameter and the second chamber volume, respectively, the second pump stage further comprising a second inlet channel and a second outlet channel each in fluid communication with the second chamber,
• wherein, for each of the first and second inlet channels, a parallel fluid path configuration of an inlet check valve and a bypass valve is disposed on the inlet channel and wherein the inlet check valve enables a forward flow of a liquid during an intake stroke and prevents a reverse flow of the liquid during a delivery stroke;
• and
• a plunger comprising:
• a first plunger section having a first plunger diameter, a first end configured for coupling to a drive mechanism, and a second end opposite to the first end, the first plunger section at least partially disposed in the first chamber;
• and
• a second plunger section having a second plunger diameter that is less than the first plunger diameter, a third end in contact with the second end of the first plunger, and a fourth end opposite to the third end, the second plunger section at least partially disposed in the second chamber, wherein a linear motion of the plunger produces a displacement volume for the first chamber that is different than a displacement volume produced for the second chamber.