Any everyday subject may trigger individual conceptions either scientifically correct or naively shaped (misconceptions, alternative conceptions). For any educator, knowledge about a pupil's individual perception may strongly support teaching success. Within this context, we see the use of drinking water as daily behavior loaded with conceptions. We monitored the perceptions of two different samples, of high achieving 10th graders and of undergraduates in Biology. All participants responded to three closed and three open questions requesting individual statements about drinking water. All open questions were categorized via qualitative content analysis mainly revealing the perception of drinking water as a clean product, precisely controlled and drinkable with no need for worry. In general, some alternative conceptions did not seem differ in both samples over the time of about five years: For instance, many see our drinking water as purified in sewage plants. However, differences between individuals exist: For example, whether water is consumed as tap or bottled water. Here, some name water hardness as the reason to not drink tap water, because they think it is harmful (although the very same participants prefer bottled mineral water). Other conceptions seem to change over time, such as the estimation about the remaining time until our drinking water might be used up, or familiarity with the term "virtual water". Summing up, we did find a positive attitude towards national drinking water policy, although major knowledge gaps need its mentioning. The relevance of these results and strategies for public and school teaching are discussed.