Within this UV Sanitizer, the UV bulb gives off Ultraviolet light wave emission when lit and causes a wavelength that when bacteria, protozoa, viruses, algae spores, or other single celled waterborne microorganisms in the incoming water flow are exposed to the light waves of the UV bulb for a proper period of time, the DNA of the microorganism is altered or disrupted and this controls and eradicates these unwanted contaminates and renders them harmless. More or less, it keeps your water clear and clean.