The article deals with the application of risk analysis methods to the problems of the drinking water supply by public water supply systems. The examples of a risk analysis and the prioritization of proposed corrective measures are demonstrated on the example of a small municipal water supply system. Within the project WaterRisk a detailed methodology for risk analysis of public water systems was developed, which was subsequently fully implemented in a WaterRisk.cz software tool. With the help of this software the risk analysis can be performed atlarge - complex water supply systems, as well as at the small ones - simple public water supply systems, for which the methodology is specially adapted. The result of a risk analysis is among other things also a list of remedial measures which have to be implemented in the water system in order to eliminate the identified risks. The tool was developed with a focus on prioritizing of these remedial measures, while maintaining a comprehensive approach and perspective. The practice shows that it is not possible for operators, respectively, owners of public water supply system, to eliminate all risks simultaneously. It is necessary to complete these steps gradually and split them for the longer time period. It is also necessary to take into account a wide range of external influences and circumstances that enter into the decision-making process. In the case of investment events it is usually about challenging economic projects, which play a decisive role. The decision support system based on risk analyses in this processes offers interesting possibilities of the use. Using a developed methodology is presented in the paper on a case study of a small public water system in the Czech Republic.