Floor drain

A floor drain assembly, comprising:

• a drain body, having a generally rectangular upper portion defining an inlet aperture, and a circular lower portion defining an outlet in fluid communication with the inlet aperture, the lower portion having helical threads configured to threadedly interconnect with an underdrain, whereby a height of the inlet can be adjusted by rotating the drain body about a central axis, and the upper portion including an integral grout rim surrounding the inlet and having a knife-tapered top edge, and further including an undercut rim around an outer perimeter of the inlet, the undercut rim having a bottom surface angled radially outward and downwardly from the drain body, and dovetail-shaped buttresses extending outward from the drain body, having tapered surfaces angled toward the drain body, thereby to mechanically interlock the drain body with hardened grout there around;
• a generally rectangular drain grate, having a plurality of drain openings, surrounded by the grout rim and supported by the drain body;
• and
• an underdrain attached to the outlet of the drain body.