Hospital tap water is a potential source of pathogenic bacteria associated with nosocomial infections. Infection control should include preventive measures to reduce the risk of waterborne infection. The efficiency of point-of-use water filters in infection control was assessed in the intensive care unit of a Hungarian hospital with long history of nosocomial Pseudomonas aeruginosa cases. All taps in the unit were fitted with disposable point-of-use filters. The incidence of nosocomial P. aeruginosa infections decreased from 2.71 to 0 cases/100 patient days when the filters were in place. Legionnaires' disease was not observed either during or outside the study period. Before the application of the filters, both P. aeruginosa and Legionella sp. were shown to colonize five of the seven taps. Filtration eliminated both bacteria completely, though secondary contamination was observed. Total genome restriction profiling of environmental and clinical P. aeruginosa isolates have shown the ubiquitous presence of a single genotype. The same genotype was detected in five of the seven previous nosocomial cases, which supports the assumption of water-derived infection. The results demonstrate that point-of-use filters are effective and cost-efficient measures in reducing health-care associated infections.