Legionellosis is a serious respiratory disease caused by the bacterium Legionella pneumophila. Although it is not transmitted from person to person, its spread through poorly maintained water systems makes it a real risk for businesses across all sectors.
Any business with domestic hot water (DHW) systems, cooling towers or spray-type irrigation systems has a legal obligation to prevent its proliferation. And the consequences of failing to do so go well beyond a fine.
Where Legionella thrives
Legionella develops in stagnant water at temperatures between 20 C and 45 C. The most critical points in an installation are:
- DHW storage tanks with insufficient temperatures or dead zones without circulation.
- Cooling towers and evaporative condensers, where water is atomised and can generate contaminated aerosols.
- Dead-end pipe sections, where water remains stagnant for days or weeks.
- Shower heads and taps that are rarely used, especially in hotels, gyms and residential facilities.
The bacterium needs nutrients (biofilm, sediment, limescale) and warm temperatures to multiply. Eliminating these conditions is the foundation of any prevention strategy.
What the regulations require: Royal Decree 487/2022
Spanish Royal Decree 487/2022 updated the previous regulation and strengthened obligations for the owners of at-risk installations. Key provisions include:
- Mandatory registration of at-risk installations with the competent health authority.
- A documented and up-to-date Legionella Prevention and Control Plan (PPCL), which must include a risk assessment, maintenance programme and action protocol.
- Periodic water testing to detect the presence of the bacterium.
- Water treatment with authorised biocides or validated physical methods.
- A record of all actions carried out, which must be kept for at least five years.
Non-compliance can result in significant financial penalties and, in the event of an outbreak, criminal liability for the installation owners.
Temperature: the first line of defence
Thermal control is the most effective and direct preventive measure. The regulations establish clear criteria:
- DHW storage: water must be maintained at a temperature equal to or above 60 C in the storage tank.
- Distribution: the temperature at the most remote point on the network must not drop below 50 C.
- Recirculation return: must exceed 50 C.
These values ensure that the bacterium cannot survive in the circuit. To achieve this, the DHW production system must be correctly sized and the distribution network must have no sections where water cools below the safe thresholds.
Practical prevention measures
Beyond strict regulatory compliance, there are good practices that significantly reduce risk:
- Eliminate dead-end pipe sections that are not in regular use.
- Periodically flush taps and showers that are rarely used.
- Clean and disinfect storage tanks at least once a year.
- Monitor the quality of the incoming water supply to minimise sediment accumulation.
- Install thermostatic mixing valves at points of use to prevent scalding while maintaining high temperatures in the network.
Professional maintenance makes the difference
Legionella prevention is not a one-off task but a continuous process that requires technical expertise, calibrated measurement equipment and rigorous record-keeping.
At Acoval we design, install and maintain DHW systems in full compliance with Royal Decree 487/2022. We work with residential communities, hotels, care homes, industrial facilities and any installation that requires reliable hot water quality control.
If you need to review the condition of your installation or implement a prevention plan, our technical team can advise you.
