Legionnaires' disease is a severe pneumonia caused by inhalation of IMPORTANCE: This study is of critical importance as it provides a comprehensive evaluation of the sensitivity of various ISO 11731:2017-standardized methods for detecting Legionella in hospital water systems-a key concern in infection prevention. Given the high variability in recovery rates across different techniques and the limitations posed by adjacent flora, the study offers valuable insights into optimizing laboratory protocols. By analyzing 276 water samples using six techniques and their combinations, the researchers highlight the superiority of methods involving concentration, membrane filtration, and heat treatment-particularly those using GVPC medium. These findings not only support evidence-based recommendations for routine environmental surveillance in healthcare settings but also help laboratories balance accuracy, cost, and resource allocation. The study's implications are especially relevant for institutions housing vulnerable populations, where early and reliable Legionella detection is essential to prevent potentially fatal outbreaks of Legionnaires' disease.