The Swimline HydroTools 87503 automatic chlorinator will reduce the time spent maintaining proper chlorine levels by supplying the exact amount needed. The durable, corrosion proof canister holds up to 9 lbs of chlorine...equaling about 8 to 9 weeks of 3" chlorine tablets. A dial control valve allows for easy regulation of the amount of sanitizer entering your pool. The Off-Line Automatic Chlorinator Installs easily to new or existing equipment and sanitizes pools up to 40,000 gallons.