Abstract: The invention relates to apparatus (1) for monitoring the level of a liquid within a vessel (3). The apparatus comprises a surface following sensing head (5) adapted to follow the surface (7) of the liquid. A gauging head (9) is mounted outside the vessel (3) at pre-determined fixed distance from the vessel (3). Rotatably mounted within the gauge head (9) is a reel (11) which has wound upon it a flexible elongate tape (13) having its free end (15) connected to the sensing head (5). The flexible tape (13) passes along a defined path of fixed length from the reel (11) to a reference point above the vessel and includes a plurality of level markers (17) which are equally spaced one from another along the length of the tape (13) each pair of adjacent markers (17) being of pre-determined fixed distance apart. A stepper motor (19) is mounted within the gauging head (9) and coupled to the reel (11) to rotate the reel (11) about its axis in two opposite directions.