Rainbow™ feeders not only save time but also reduce manual handling of chemicals. They use large or small trichlor or bromine slow-dissolving tablets to make sanitizing your new or existing pool or spa easy and automatic. Both install easily on the pressure side of the pump, downstream of the filter and heater. The freestanding Model 300 feeder feature an external fine-control valve that lets you adjust the feed rate to meet specific pool or spa requirements. The Model 300 feeder is ideal for retrofitting existing pools for automatic sanitization. The feeder extensions increase tablet or stick capacity, so you can vacation without worrying about running out of chlorine