The presently disclosed technology generally provides a modular support system for plumbing connections. In one example, the system includes a frame, a connector that fits entirely in front of a support stud, and an optional housing. The frame includes symmetrical sides, each including a rail assembly. The connector includes first opposed sidewalls, each having a pair of boxways that receive the rails on any side of a frame unit to form a sliding joint between the frame and connector. Second opposed sidewalls include flexible tabs that engage frame corner flanges to prevent rearward disengagement of the connector from the frame. The housing includes structure for connection with the frame. The housing can be rotated for connection with the frame to receive vertical or horizontal plumbing lines. Connectors can connect the frame units in vertical or horizontal relation, or on either side of a building stud, or to brackets.