Abstract: An animal caging system has a plurality of stackable support trays with integral water supply conduits to supply water sequentially to each cage and eliminate any channels of stagnant water. Each support tray includes a vertical support member that engages the vertical support members of adjacent support trays in a stacked relationship, and a number of cage docking stations arranged around the vertical support member. The vertical support member includes a water supply conduit that extends to each cage docking station of the support tray and has openings in fluid communication with corresponding openings in the water supply conduits of adjacent support trays. In this manner, the water supply conduits of the stacked vertical support members combine to supply water in a single flow path to the cage docking stations on each support tray.