PURA’s ultraviolet sterilizers ensure that your water stays clean and pure. Regular tap water may still contain harmful microorganisms, which can pose a threat to children, older adults, people with compromised immune systems and sometimes even healthy adults. PURA ultraviolet sterilization systems eradicate these hazards, giving homeowners an affordable and safe alternative to bottled water. Ultraviolet sterilizes water by emitting just the right level of radiation to kill microbes such as viruses, bacteria, algae and mold. This level of radiation is so low, that it leaves no trace in the water and poses no health hazard to people. A UV water filter uses a simple light bulb as the source of its UV light. The light bulb should be changed annually for maximum effectiveness.