Community water supply systems must monitor fluoride levels in there systems whether or not they fluoridate. Systems that draw their water from surface supplies must sample at least once per year (1). Water drawn from ground water supplies must be sampled once every three years (1). Sampling rates vary between plants and are determined by state inspectors. Frequency of sampling may be increased or decreased depending on the probability of a system exceeding MCL limits.
Sampling of water supply systems must be accomplished in such a manner as to be representative of the levels that would be found at a household water tap. Samples must be taken at each individual water source and must be representative of the maximum fluoride level that has the possibility of occurring. Water samples are tested for fluoride with one of three methods: automated ion-selective electrode, ion-selective electrode, complexone, or colorimetric SPADNS (1). A sample exceeding the maximum MCL must be reported to the state within seven days of sampling. Three additional samples must then be taken at the same tap within a month. Four separate analyses determine a systems level of compliance (1).