A dishwasher appliance includes a wash tub defining a wash chamber, a sump housing defining a sump for collecting wash fluid, the sump housing defining a drain basin, and a fluid circulation assembly positioned within the sump. The fluid circulation assembly includes a drain cover seated within the drain basin, a wash pump assembly seated on top of the drain cover, a filter cleaning manifold positioned over the wash pump assembly, and a plurality of mechanical fasteners that pass through filter cleaning manifold and into the sump housing to attach the filter cleaning manifold to the sump housing and to secure the wash pump assembly and the filter cleaning manifold within the sump.