The Drinking Water Inspectorate has provided the following information about the assessment of the single sample result on 6 July 2000.
The natural level of fluoride in the source water is between 0.07 and 0.25 mg/l (the European maximum level permitted is 1.5 mg/l). There is no additional fluoride put into the water at the treatment works. The single adverse result recorded on 6 July probably arose as a consequence of an error in the sampling/analytical process. However this could not be proven conclusively. All samples in the nine years since 6 July 2000 have given satisfactory results.