Enriched [ 18 O]-water is the target material for [ 18 F]-fluoride production. Due to its high price and scarce availability, an increased interest and necessity has arisen to recycle the used water, in order to use it multiple times as a target material for [ 18 F]-fluoride production. This paper presents an efficient treatment and reprocessing procedure giving rise to high chemical quality [ 18 O]-water, thereby maintaining its enrichment grade. The reprocessing is subdivided into two main steps. In the first step, the [ 18 F]-FDG (fluorodeoxyglucose) synthesis preparation was modified to preserve the enrichment grade. Anhydrous acetonitrile is used to dry tubing systems and cartridges in the synthesis module. Applying this procedure, the loss in the enrichment throughout the reprocessing is <1%. The second step involves a fractional distillation in which the major part of the [ 18 O]-water was recycled. Impurities such as solvents, ions, and radioactive nuclides were almost completely separated. Due to the modified synthesis preparation using acetonitrile, the first distillation fraction contains a larger amount of an azeotropic