The knowledge base of the distinct disciplines grows incrementally. A high variety of the knowledge acquisition (KA) techniques can be applied at specific domains. In this paper we introduce some KA practices related to historical watermills. The different methods complement each other, none of them is fully comprehensive (visual assessment, parts of former machines, personal inquiry, landscape check, markers, signals, geographic forms, etc.). We could set up new ontology categories on the categorization of these technical relicts. It demonstrates the applicability of these wide spread manners, so these methods are recommended also for other fields such as archeology or technical history.