A cage nut assembly for a drain pan includes a nut having a barrel with a barrel end and a distal end opposed thereto. A flange at the distal end has a flange face abutting the drain pan inner surface. A threaded bore is defined along a central axis through the barrel and flange. At least one channel is defined in the flange face and allows substantially complete drainage of a fluid from a sump through a single drain aperture. A cage having a plate with a central aperture receives the barrel with substantial clearance to an edge of the central aperture. Leg(s) extend substantially orthogonally from the plate. An attachment projection on the leg(s) attaches the assembly to the drain pan. The assembly accepts a flange bolt removably installed through the single drain aperture. The flange bolt removably compresses a seal around a periphery of the single drain aperture.