Legionella control in the water system of antiquated hospital buildings by shock and continuous hyperchlorination: 5 years experience.

Background: To control the presence of Legionella in an old hospital water system, an integrated strategy of water disinfection-filtration was implemented in the university hospital Umberto I in Rome.

Methods: Due to antiquated buildings, hospital water system design and hospital extension (38 buildings), shock hyperchlorination (sodium hypochlorite, 20-50 ppm of free chlorine at distal points for 1-2 h) followed by continuous hyperchlorination (0.5-1.