Fluoride is widely added to drinking water systems to help prevent tooth decay. It is normally added in the form of liquid hydrofluorosilicic acid, which can be easily handled and applied using standard metering pumps. While control of the fluoridation process is easily handled by simple flow proportional feed, water quality monitoring of final fluoride concentrations is useful in providing an alarm in the case of overfeed problems. Optimum fluoride levels of around 1 PPM are safe, but control system problems resulting in concentrations above 2 PPM are considered excessive and need to be detected as early as possible. Loss of chemical feed can also be detected quickly and reliably with on-line fluoride monitoring. 

The Q46F provides continuous water quality monitoring of free fluoride concentration in potable water. The system employs a fluoride sensitive ion selective electrode (ISE) which provides reliable measurement down to 0.1 PPM and as high as 1000 PPM. A chemistry module provides sample conditioning for the sensor and the measured fluoride concentration is displayed on a separate electronics module that also provides alarm and analog output functions.