Legionella testing in water intended for human consumption

Legislative Decree no. 102 of June 19, 2025, which entered into force on July 19, 2025, introduced significant changes regarding the quality of water intended for human consumption.

Regarding microbiological quality, the measure mandated compliance with the Guidelines for the Prevention and Control of Legionellosis (May 7, 2015); while previously considered recommendations, these have now become binding regulations for a range of entities.

The entities covered by Legislative Decree 102/2025 include:

• Healthcare, social-health, and social-care facilities (both inpatient and outpatient)
• Hotels and other accommodation facilities, campsites, correctional facilities, ships, stations, and airports
• Public and collective catering services, including corporate (public and private) and school canteens
• Barracks; educational institutions with sports facilities; gyms; sports, fitness, and wellness centers (spas); and other facilities for collective use (e.g., beach resorts, large water parks, pools with water features, theme parks)
• Condominiums

What Legislative Decree 102/2025 mandates

Legislative Decree 102/2025 amends and supplements the previous Legislative Decree 18/2023, transposing European Directive (EU) 2020/2184, which regulates the quality of water intended for human consumption. The measure extends and tightens water safety and quality requirements, placing particular emphasis on the management and monitoring of *Legionella*—the bacterium responsible for legionellosis, a serious pulmonary infection.

Legislative Decree 102/2025 formalizes the requirement to identify and appoint an Internal Water System Manager (GIDI)—the party responsible for managing legionellosis risk—thereby ensuring monitoring and prevention within internal water systems.

RELEVANT PARAMETERS FOR RISK ASSESSMENT AND MANAGEMENT OF INTERNAL DISTRIBUTION SYSTEMS (ANNEX I, PART D):

• Legionella spp. < 1000 colony-forming units (CFU)/L

SPECIFICATIONS FOR PARAMETER ANALYSIS (ANNEX III, PART A)

The analytical method for Legionella is ISO 11731, in compliance with the value established in Annex I, Part D. In addition to the monitoring associated with risk assessment, and to supplement culture-based methods, other methods may be used—such as rapid culture methods, non-culture methods, and molecular methods (including qPCR, performed in accordance with ISO/TS 12869).