What is the most common type of pump?

The most common type of pumps are Positive displacement and Non positive displacement pumps.

Explanation:

Pumps are two types:

(A) Positive displacement pump

(a) Gear pump

(1) Ge rotor pumps

(2) Internal gear pumps

(3) Lobe pumps

(4) External gear pumps

(b) Piston pump

(1) Radial piston

(2) Axial piston

(c) vane pump

(B) Non positive displacement pump

(a) Centrifugal pump