Objectives: The aim of this study was to identify the correlation between adequate water intake and the prevalence of metabolic/heart diseases. Methods: We analyzed the data from the 2012 Korea National Health and Nutrition Examination Survey. All participants were divided into Group Above Adequate Intake (n = 736) and Group Below Adequate Intake (n = 4,819) according to water intake. The thresholds were 1.8 L for men and 1.4 L for women based on the World Health Organization report findings. Logistic regression analyses were performed to verify the correlation between water intake and prevalence of hypertension, diabetes mellitus, dyslipidemia, myocardial infarction, and angina pectoris. Results: There were significant differences between the two groups in terms of the following variables: age, smoking, alcohol, stress, dietary supplements, body weight, physical activity, total calorie intake, water intakes from food, and sodium intake. Participants in Group Above Adequate Intake showed a higher prevalence of hypertension [odds ratio (OR) = 1.22; 95% confidence interval (CI), 0.58–2.55], diabetes mellitus (OR = 1.38; 95% CI, 0.51–3.73), angina pectoris (OR = 0.94; 95% CI, 0.47–1.86), and myocardial infarction (OR = 5.36; 95% CI, 0.67–43.20) than those in Group Below Adequate Intake, whereas the latter showed a slightly higher prevalence of dyslipidemia (OR = 2.25; 95% CI, 0.88–57.84) than the former. Conclusion There was no statistically significant association between water intake and any of the metabolic/heart diseases. However, further studies on water intake are needed to confirm our findings.