A controller for a water related system, the controller being configured to control a characteristic of water flow in the water related system, the controller comprising: a control unit comprising a sensor and a housing, the sensor comprising an emitting unit configured to emit a signal and a detecting unit configured to detect the signal, wherein the sensor is optical, infrared or ultrasonic; and an input member arranged to rotate around a main axis of the controller and being rotationally movable relative to the control unit, the input member or the control unit comprising a reflector arranged to reflect the signal towards the detecting unit, wherein the input member is separate from the housing and moves independently of the control unit, the environment in the housing of the control unit being controlled to reduce the impact of the surrounding wet environment on the sensor, and the components of the control unit being sealed within the housing and therefore protected from the wet environment; wherein the input member is movable relative to the control unit between a neutral position and a displaced position or multiple displaced positions, the movement of the input member being rotation of the input member around the main axis of the controller; wherein the controller is configured to determine the position of the input member based on the reflected signal; and wherein the controller is configured to determine an input based on the position of the input member; further comprising at least one of: a mechanical spring configured to apply a force to return the input member to the neutral position and at least one magnet pair configured to apply a force to return the input member to the neutral position. a control unit comprising a sensor and a housing, the sensor comprising an emitting unit configured to emit a signal and a detecting unit configured to detect the signal, wherein the sensor is optical, infrared or ultrasonic; and an input member arranged to rotate around a main axis of the controller and being rotationally movable relative to the control unit, the input member or the control unit comprising a reflector arranged to reflect the signal towards the detecting unit, wherein the input member is separate from the housing and moves independently of the control unit, the environment in the housing of the control unit being controlled to reduce the impact of the surrounding wet environment on the sensor, and the components of the control unit being sealed within the housing and therefore protected from the wet environment; wherein the input member is movable relative to the control unit between a neutral position and a displaced position or multiple displaced positions, the movement of the input member being rotation of the input member around the main axis of the controller; wherein the controller is configured to determine the position of the input member based on the reflected signal; and wherein the controller is configured to determine an input based on the position of the input member; further comprising at least one of: a mechanical spring configured to apply a force to return the input member to the neutral position and at least one magnet pair configured to apply a force to return the input member to the neutral position.