Introduction: In practice, public institutions have been dealing with the problem of the presence of Legionella bacteria in the internal water supply network for many years. Control of the number of bacteria in drinking water supply systems is not only based on knowledge of microorganisms, but also on the identification of risk factors for Legionella reproduction within the systems. The care for the proper hygienic maintenance of the water supply system is left to the institutions themselves. The greatest influence on the appearance of Legionella in the system has the water temperature and the choice of material from which plumbing systems are made. Purpose: The purpose of this master's thesis is to determine the influence of the materials of internal water supply systems on the reproduction of Legionella bacteria in public buildings in central Slovenia. Methods: By reviewing the professional and scientific literature, we obtained information on the influence of materials on the reproduction of Legionella bacteria in internal water supply networks. We identified public institutions in central Slovenia, which we invited to participate. The research itself consisted of two parts, obtaining data with a questionnaire and processing existing data on the number of Legionella bacteria in water samples from selected institutions.Results: The results showed that elevated levels of Legionella spp. identified in older buildings, where consequently older materials made of galvanized iron pipes and galvanized iron pipes in combination with plastic materials are installed. The highest concentrations of Legionella spp. have occurred where appropriate preventive measures have not been provided and implemented. The share of positive samples was 34%. In institutions where only plastic materials (PEX and PVC) are installed, the share was positive 2%. The research shows that the preventive implementation of measures showed positive results at the first re-sampling in 32% of public buildings where the bacteria Legionella spp. we no longer identified. We find that the measure with thermal disinfection was successful. Respondents state in their answers that they most often use thermal disinfection and perform consistent water dispensing to prevent the presence of the bacteria in question. Discussion and conclusion: Plumbing in public buildings or in the home water supply network (HVO) represents a complex temporal, dynamic and spatial diversity. In this case, the drinking water is considerably influenced by the materials of the installation wiring. All materials have certain advantages and disadvantages for the growth of microorganisms.
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