This ultraviolet lights breaks DNA structure of microorganisms and makes them inactive unaffected. By this way, %99,9 average ratio of disinfection productivity is supplied.. To be able to kill microorganisms with this system, Ultraviolet light must directly hit over them. For this reason, before water enters in ultraviolet system, parameters such as sediment, cloudiness must be removed from water. Sand filter or cartridge filters are recommended to be used before ultraviolet. To obtain good productivity from ultraviolet units, periodical maintenance is important. UV lamb change once a year and periodical Quartz glass cleaning depending on raw water quality must be made. In case, if this cleaning is not done, UV light affect and output of equipment will decrease.