Legionella: prevention and monitoring in water systems

Updated on 2026-07-06

What Legionella is, who must assess the risk, how sampling and analyses are carried out and which prevention and remediation measures to adopt: the guide for hotels, care homes, healthcare facilities and businesses with water systems.

What Legionella is and where it develops

Legionella is a bacterium that proliferates in water systems under certain conditions (stagnant water, temperatures between 20 and 50 °C, presence of biofilm and scale). It can spread via aerosols (showers, cooling towers, air-conditioning systems) and cause respiratory infections.

Who must assess the risk

The national guidelines for the prevention and control of legionellosis (State-Regions Agreement) require a risk assessment especially for hospitality, healthcare facilities, care homes, spas, gyms and collective systems. It is the manager's responsibility to prepare the assessment and a register of interventions.

Sampling and laboratory analyses

Monitoring involves water sampling and analysis at an accredited laboratory for the detection of Legionella, at a frequency defined according to the risk level. The results guide the interventions and must be kept in the register.

Prevention and remediation measures

Prevention is based on correct system management: temperature control, reduction of stagnation, removal of scale and biofilm, disinfection treatments (thermal or chemical). In case of contamination, targeted remediation interventions are carried out.

How Dipres supports Legionella monitoring

With RistoHelp Consultant we rely on a certified laboratory for environmental investigations: we support risk assessment, sampling, analyses according to the guidelines and the definition of prevention and remediation measures, with the necessary documentation.

Frequently asked questions

Is the Legionella risk assessment mandatory?

For at-risk facilities (hospitality, healthcare, care homes, spas, etc.) the national guidelines require a risk assessment and its documented management: it is the manager's responsibility.

How often should sampling be done?

The frequency depends on the system's risk level and is defined in the risk assessment; it must be updated based on the results and interventions carried out.