Water monitoring has an unquestionable value for people's safety. Despite this, most systems are expensive to operate due to high power consumption or high measuring time. This translates to an inefficient system. This study proposes a design for a low power consumption system to monitor water quality. By using a simple 3D printed design that includes UV LEDs, a filter, a lens and a photosensor. The tests performed in this paper is to show the effect the lens provides and the limited power consumption of the overall system as well as the sensitivity of the system.