Manganese and iron are essential nutrients necessary for the normal functioning of the organism, while long-term exposure to elevated concentrations, especially through drinking water, can cause serious health conditions. The modified construction of the Ponikve reservoir at the source of Vela Fontana in the summer months leads to the creation of anoxic conditions, due to which an increased concentration of manganese and iron naturally occurs in the raw water. Since such water requires a complex process of conditioning by aeration before consumption, the aim of this paper is to show the concentrations of manganese and iron in drinking water over a five-year period on the island of Krk. In that period, a total of 352 samples were analyzed according to the HRN EN ISO 17294-2:2016 standard using inductively coupled plasma- mass spectroscopy. In none of the samples analyzed did the concentration of manganese and iron exceed the M.D.K. prescribed by the Pravilnik o parametrima sukladnosti, metodama analize, monitoringu i planovima sigurnosti vode za ljudsku potrošnju te načinu vođenja registra pravnih osoba koje obavljaju djelatnost javne vodoopskrbe (NN 125/2017). The results indicate that there is no periodicity in the occurrence of elevated metal concentrations depending on the month, which indicates that the conditioning procedure is very effective. Long-term consumption of such water does not pose a public health risk for the general population.