We sought to explore perceived strengths and weaknesses of surveillance systems for the detection of drinking-water-related illness in Europe based on the experience of individuals utilising such systems. We designed and conducted a qualitative semi-structured interview study with thematic analysis. Interviews took place in six European countries with seven experts in epidemiology, water and public health. Interviewees remarked upon variation between and within countries in laboratory and sampling protocols and reporting practice; these were felt to influence timeliness and sensitivity of laboratory- and clinician-report-based surveillance. Electronic reporting, reminders to report and direct report relay to national level were considered strengths of report-based surveillance. A need was expressed for more detailed case demographic information to facilitate outbreak detection. Existing infrastructure permitting, prescriptions data, anti-diarrhoeal pharmaceutical sales, absenteeism and consultations were cited as useful outbreak indicators. Information regarding consumer water quality complaints was highlighted as a potentially useful data source. Collaboration with water companies (concerning water distribution and incidents), and constructing and maintaining relationships with local and external data providers were cited as requisites of effective surveillance. Inter- and intra-organisational collaboration and information integration are likely to improve surveillance, leading to more astute estimates of the waterborne disease burden.