Various types of operating ultraviolet disinfection reactor designs were evaluated for hydraulic characteristics and cleaning requirements. The fluorocarbon polymer tube designs promote plug-flow behavior because of their relatively high length-to-diameter ratio. Hydraulic evaluations of two different types of relatively current quartz tube designs demonstrated significant short-circuiting. Historically, quartz tube units have been designed with some form of accessory cleaning device to reduce fouling. The accessory cleaning devices, either mechanical wipers or ultrasonics, were marginally effective and periodic chemical cleaning is also required.