The Florida Keys Aqueduct Authority (FKAA) provides potable water to the residents of Monroe County through a 130-mile long transmission pipe and 650 miles of distribution system piping. The FKAA's water treatment plant is located in south Dade County and treats an average of 14.0 million gallons per day. For systems using a chloramine disinfectant residual, the threat of nitrification is of great concern and can present significant distribution system operating problems. A nitrification episode can lead to loss of combined chlorine residual, increased heterotrophic plate count, increased positive total coliform and loss of consumer confidence if public notification is required. This paper presents the challenges that nitrification presented to the FKAA system and the control strategies employed to control the problem.