There is provided a water supply control system for a tap (2). The control system includes a spindle (16) attached at one end to a tap handle (10) and at its other end to a tap rotation detector/valve actuator, the spindle (16) extending through the water supply conduit (3) to a tap rotation detector (5) which sends a signal to a supply valve (4) via a controller (6). The controller (6) triggers closure of the valve (4) if the valve has remained open for a predetermined time interval. The control system also has a detent to limit rotation of the spindle (16) in a tap closing direction.