A system of supply valves according to the present invention may include a first and second supply valve, each of which is connectable to a terminal end of a water supply line so as to provide direct access to the water supply. The system may be disposed within a modular plumbing supply box, and the valves may be spaced from one another by a reduced separation, X1. Each supply valve of the system may further include a top portion and bottom portion that are interconnectable and which form a water-proof seal therebetween. The top portion may comprise ridges that cooperate with channels of the bottom portion when the two portions are interconnected to form passageways. The top and bottom portions may be positionally and rotationally locked to one another, for example, using a wireform clip and inserting legs of the wireform clip through the passageways.