Abstract: A water line adapter designed to convert a single water outlet line into a multiple outlet water line, with the adapter comprising a cubical body, a captive rotatable threaded nut attached to one face of the body, a first threaded member attached to the opposite face, and a second threaded member attached to another face. In one application, the adapter is attached to a shut-off valve by threading the captive rotatable nut over the threaded member of the shut-off valve. In this manner, a single outlet shut-off valve can be converted into a shut-off valve having two outlets. The adapter is particularly useful in providing a water supply to appliances such as ice makers, dishwashers and under-the-counter water filters.