Years of customer use and satisfaction have proven Rainbow feeders to be the performance leader in pool & spa chemical dispensers. FEATURES 300 and 320 series filters available in clear amber for easy tablet level monitoring. Completely enclosed system - no special venting required. No escaping gases. 50 PSI maximum operating pressure. In-Line Feeders. 320 Series. For permanent installation in return line of new or existing pools or spas. Installs in return line on pressure side of pump downstream of all equipment. Standard with 2 in. slip PVC fittings and adapters for 1-1/2 in. Off-Line Feeders. 300 Series. Retrofits into existing pools or spas. Operates on pressure side of pump. Uses 1/4 in. feeder hoses, control valve and fittings. Note: Rainbow Automatic Chlorine/Bromine feeders are for use with slow dissolving trichlor or bromine tablets only. Model 300 Offline Chlorine Feeder holds 11 large or 98 small tablets. Treats 12,000 to 48,000 gallons.