Abstract: A valve monitoring switch is operated by an adjustable length rod whose end senses the position of a valve, for example, a water supply valve. The rod, enclosed by an assembly-mounting nipple, is so pivot-mounted as to be capable of movement in a planar arc, whose plane is substantially coincident with or parallel to the component of valve movement as between its open and closed positions. When the rod is pivoted through a small arc of movement, against the bias of conventional electrical switches, they signal the valve position or its change. To effect installation without damage to the switch assembly, an angularly adjustable mounting socket for the nipple is provided; also, the rod length is adjustable, so that during installation it may be retracted alongside the electrical switch assembly; and after installation may be extended to and fixed in a position in which it will sense the state of the valve.