Pump and hydraulic unit of a pump

A hydraulic unit of a pump configured for pumping liquid comprising solid matter, the hydraulic unit comprising:

• a housing defining a volute and an impeller seat located in the volute;
• the housing having an axial inlet opening and an outlet opening,
• the impeller seat having an axial inlet defined by an inlet wall,
• the impeller seat having an inlet radius (R) measured from an axially extending centre axis (A) to a circular intersection between the inlet wall and an upper surface of the impeller seat;
• and
• the impeller seat comprising a guide pin connected to and extending radially inwards from the inlet wall;
• the guide pin having a tip radius (r) measured from an axially extending centre axis (A) to a radially innermost part of the guide pin, and
• the housing comprising a cut water,
• an imaginary 15%-circle offset radially inwards from the circular intersection fifteen percent of the difference between the inlet radius (R) and the tip radius (r);
• a cut water line defined by a radius of the impeller seat tangent to a most downstream point of the cut water, viewed in a direction of rotation of the pump, the cut water line located downstream a radius of the impeller seat perpendicular to the outlet opening, viewed in the direction of rotation of the pump;
• and
• a guide pin angle (μ) between the cut water line and a radius of the impeller seat intersecting a leading edge of the guide pin at the imaginary 15%-circle, viewed in the direction of rotation of the pump, is equal to or more than 3 degrees and equal to or less than 25 degrees.