Waterborne infections are highly probable in cases when there are failures to prevent the faecal contamination of drinking water. The majority of such cases take place at relatively small groundwater abstraction plants utilizing minimal water treatment, and the source of contamination often remains unclear. The fast and reliable detection and confirmation of microbial drinking water safety is essential in the protection of public health and even a very low concentration of faecal bacteria needs to be detected. In a recent study, the hazards to the microbial safety of drinking water were estimated at small community water supplies in central Finland. The results showed that faecal indicator bacteria could be detected in 10 % of the groundwater samples originating from five water supply plants, all of them serving less than 250 consumers. The main on-site hazard identified to reduce water safety was insufficient protection against the influence of surface water indicated by a poor well construction and maintenance, an insufficient depth of the protective soil layer above the groundwater table or the possibility of uncontrolled river or lake bank infiltration. In the future, a multiple parameter microbial hazard identification with a wide set of indicators during an intensive sampling period might raise awareness of the possible health risks at small water supply plants. As a preventive measure, the upgrading of the water treatment processes, utilization of disinfection and systematic risk management at small groundwater supplies are recommended.