Fluid circulation system for dishwasher appliances

A fluid circulation system for a dishwasher appliance, the dishwasher appliance defining a vertical direction, a lateral direction, and a transverse direction which are mutually orthogonal, the dishwasher appliance comprising a tub that defines a wash chamber, the fluid circulation system comprising:

• a sump positioned below the wash chamber along the vertical direction for receiving fluid from the wash chamber, the sump comprising a chamber having a sidewall and a base wall;
• a pump, the pump comprising an impeller disposed within the chamber;
• and
• a filter disposed within the chamber and surrounding the impeller, the filter comprising a sidewall extending along the vertical direction between the base wall of the chamber and a top wall of the filter, the sidewall of the filter spaced from the sidewall of the chamber and radially aligned with the impeller, the sidewall of the filter defining a plurality of perforations extending therethrough, individual volumes of each of the plurality of perforations increasing along the vertical direction from the base wall of the chamber;
• wherein a volume within the filter is greater than a volume between the sidewall of the chamber and the sidewall of the filter at any given height from the base wall.