An apparatus measures a fluid level in a container. A light source emits a light beam. A light sensor can sense the light beam. An optical conduit is arranged in a container for holding fluid. The optical conduit is arranged between the light source and the light sensor along a path of the light beam, such that at least one part of the light beam passes through the optical conduit, and at least an other part of the light beam passes through the fluid when the container holds the fluid. The sensor senses the light beam when a level of the fluid coincides with the one part of the light beam passing through the optical conduit, and the sensor does not sense the light beam when the level of the fluid coincides with the other part of the light beam passing through the fluid due to internal reflection at the fluid level.