Features 300 and 320 series filters available in clear amber for easy tablet level monitoringCompletely enclosed system - no special venting requiredNo escaping gasesAll Rainbow Feeders are NSF Listed50 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. Retrofits into existing pools or spas. Operates on pressure side of pump.