The United Nations’ campaigns to ensure clean and safe water, good health and well-being, sustainable cities and communities (Sustainable Development Goals 3, 6, and 11, respectively) are interwoven. The study adopted these three SDGs to seasonally assess the available groundwater samples within the Fountain University, Osogbo, Osun State. The study sampled six locations in the dry (February 2024) and wet (May 2024) seasons in triplicate; analysed them at the Osun State Water Commission Laboratory, Ede Office, using standard procedures and methods; and subjected the obtained data to descriptive and inferential statistics, and compared their mean values with WHO (2011), NIS554 (2015), and institution-water-sampled research. The results showed that the pH (5.20 to 7.00 < 6.98 to 7.91), dissolved oxygen (2.40 to 2.80 < 4.30 to 6.50 mg/ L), alkalinity (18 to 170 < 24 to 142 mg/ L)/ total hardness (28 to 138 < 42 to 174 mg/ L)/ Ca hardness (20 to 114 < 14 to 50 mg/ L) (except at Yusufi Ali hostel), Ca (4.56 to 11.20 < 5.60 to 20 mg/ L), Sulphate (BDL to 37 < 34 to 51 mg/ L), residual-Cl (BDL < BDL to 0.21) and F (BDL < BDL to 1.45 mg/ L) were lower in the dry than wet season; carbonate (18 to 138 mg/ L) < bicarbonate (73 to 646.60 mg/ L) in the dry season; carbonate (138) and bicarbonate (646.60) were higher than the limit (100 mg/ L) at Yusuf Ali hostel in the dry season; water pH was lower than the limit, making the water sample slightly acidic at main canteen (5.20), Sambisa hotel (5.20) and Mountain (5.40) in the dry season; Fe (BDL to 1.90 mg/ L) content was higher than the limit (0.30 mg/ L) in dry season; Phosphate was BDL at Mountain, Yusuf Ali hostel, and Masjid in both seasons; turbidity (0.67 to 8.79 mg/ L) was lower than the limit (5.00 mg/ L) except at the main canteen in the wet season; K- and Cr-contents were higher than the limit (0.01 mg/ L) in both seasons; and lastly, there was possible seasonal influence on the water parameters’ variations. Having found that K- and Cr-contents were higher than the limits in both seasons, the study recommends measures to prevent possible human health risks from high levels of K and Cr in the school’s groundwater.