Pump

A pump comprising:

• an inner element having a plurality of pump bodies that pump an underground liquid, a pump shaft that extends in a vertical direction and on which the plurality of pump bodies are disposed in the vertical direction, a motor shaft that is connected to one end of the pump shaft and extends in the vertical direction, a magnetic part that is provided on an outer peripheral surface of the motor shaft, and a pump stator that has a tubular shape for accommodating the plurality of pump bodies and extends in the same direction as the pump shaft;
• a production pipe having a tubular shape extending in the vertical direction;
• accommodating the inner element inside the production pipe and supporting the inner element;
• and
• a motor stator disposed at a lower portion of the production pipe and constituting an electric motor together with the magnetic part,
• a cylindrical gap is formed between the production pipe and the pump stator,
• the pump stator has a tubular pump casing that surrounds the plurality of pump bodies,
• a penetrating portion is provided in the pump casing,
• the penetrating portion is a hole that penetrates the pump casing in a radial direction from an inside of the pump casing to an outside of the pump casing, and
• the penetrating portion is formed in a portion of the pump casing that faces a pump body, which is located in an intermediate stage of the plurality of pump bodies, in the radial direction.