Your Hayward CL-220 series automatic chlorine feeder is designed for installation next to your filter system. It operates by the pressure differential of your system which draws water through the feeder. It uses slow dissolve Trichloro-S-Triazinetrione (Tri-Chlor) large or small tablets (or sticks) ONLY. No other type of chemical should ever be used in your chlorine feeder. Your CL-220 holds up to 18 large (3" diameter) tablets (about 9 lbs.) and has a dial type control valve to regulate the rate of water flow through the chlorine feeder. This large capacity feature, under normal conditions, should provide a minimum of two weeks chlorination for large pools. By regulating the valve setting between FULL (more chlorine) and OFF (less chlorine) and the amount of Tri-Chlor tablets you place in the feeder, you can easily adjust the chlorine feed rate that is necessary to maintain the proper chlorine residual for your pool.