Efitherma

Temperatures required to eliminate Legionella in DHW: prevention for heat pumps

Autora: Araceli Buendía

Efitherma Marketing Department

Temperatures required to eliminate Legionella in DHW: prevention for heat pumps

Author:Araceli Buendía

Efitherma Marketing Department

How is Legionella prevention ensured in DHW systems with heat pumps?

The production of Domestic Hot Water (DHW) in residential buildings, hotels, hospitals and sports facilities entails a significant health responsibility. One of the main risks associated with these systems is the potential proliferation of the bacterium Legionella pneumophila, which causes legionellosis, a disease that can lead to serious respiratory infections.

In this article, we look at what Legionella is, what health regulations require, what temperatures must be reached, and how anti-Legionella cycles work in modern DHW systems.

What is Legionella and why does it pose a risk in DHW systems?

Legionella pneumophila is a bacterium that thrives in aquatic environments and can proliferate in water systems when certain temperature and stagnation conditions are present.

Transmission to humans occurs mainly through the inhalation of contaminated aerosols generated by showers, taps or spray systems.

DHW systems can become a breeding ground for such issues if factors such as the following are not properly managed:

For this reason, DHW systems must be designed and managed in accordance with specific hygiene criteria that minimise the risk of bacterial growth.

Regulations on the prevention of Legionella in DHW systems

In Spain, the prevention and control of Legionella is primarily regulated by:

Real Decreto 487/2022: Sets out the health requirements for the prevention and control of legionellosis.

This regulatory framework sets out a series of technical and health-related criteria for water installations, including DHW systems. The most important aspects include:

Water temperature control
Hydraulic design designed to prevent stagnation
Maintenance and cleaning programmes
Thermal or chemical disinfection protocols
Recording of operations and health checks

Temperature control is one of the most effective and widely used methods for preventing the growth of Legionella in DHW systems.

Temperatures to prevent the spread of Legionella

The behaviour of Legionella bacteria is closely linked to water temperature.

Water temperature	Bacterial behaviour
< 20°C	The bacterium remains inactive
20°C – 45°C	Optimal growth zone
50°C	The bacteria begin to die
60°C	Quick removal
70°C	Immediate thermal disinfection

For this reason, DHW systems must be designed to meet certain thermal requirements. Common recommendations for plumbing systems:

≥ 50°C

Temperature at terminal points

≥ 60°C

Accumulation temperature

≥ 60-70°C

Periodic thermal disinfection

These temperatures allow the presence of the bacteria in the Domestic Hot Water system to be reduced or eliminated.

Anti-Legionella Cycles: How do they work?

Anti-legionella cycles are a thermal disinfection procedure used in hot water supply systems to prevent bacterial proliferation. The process involves temporarily raising the temperature of the stored water to levels capable of eliminating the bacteria, typically between 60 °C and 70 °C, for a specified period.

This process can be programmed to run automatically in many modern DHW production systems.

Objectives of the Anti-Legionella programme

Usual frequency of performance

Depending on the installation, these cycles can be programmed:

The automation of these cycles is particularly important in hotels, hospitals or buildings with high DHW consumption, where hygiene standards must be maintained at all times.

Anti-Legionella cycle in Efitherma heat pumps

Efitherma heat pumps feature a specific, automatic anti-Legionella cycle function, designed to ensure the hygiene and safety of the DHW system through scheduled thermal disinfection.

This function allows the temperature of the stored water to be temporarily raised in order to eliminate any bacteria present in the system.

Configurable parameters for the anti-Legionella cycle

Efitherma heat pumps allow you to configure various settings to tailor the system’s operation to each installation:

The system allows you to set a disinfection temperature between:

60°C | 70°C

This range allows for the application of appropriate heat treatments tailored to the requirements of each facility.

The system allows you to schedule the cycle by selecting a date and time:

Remote control with EFI SmartApp

Efitherma heat pumps are equipped with state-of-the-art control systems, thanks to their touchscreen controller (TST Control Display) and remote management via the EFI SmartApp.

Thanks to these, you can configure settings such as the following:

This connectivity makes the work of installers, maintenance technicians and facility managers easier, enabling more efficient and secure management of the system.