No. 17 Image Shown R1722535/8 In OD 18 In Tube Used on Rainbow Pentair Chemical Feeders Chlorinator Parts Rainbow's 320 series of In-line chlorinators are designed for permanent installation in the return line of pools or spas. Plumbs into 2 inch or 1.5 inch PVC pipe. Includes threaded and slip 2" x 1.5" reducers to fit either size. Use only slow dissolving Trichlor or Bromine tablets and sticks The 320 Rainbow chemical feeder includes lid lubricant, additional hose and heavy duty control valve. The Rainbow Automatic Chlorinator is NSF listed.