Cooling towers and evaporative condensers are used in a wide range of process and energy industries where large amounts of heat must be dissipated efficiently.
Sectors such as the chemical, paper, cement, pharmaceutical, steel, and plastics industries, as well as nuclear, thermal, geothermal, and biomass power plants, and the hospital and healthcare sectors rely on these facilities to maintain their process temperatures within safe and cost-effective limits.
In Spain, cooling towers and evaporative condensers—just as with the control of sanitary systems and potable water—are directly affected by Royal Decree 487/2022, dated June 21, which establishes the sanitary requirements for the prevention of legionellosis and has been in effect since January 2, 2023.
Failure to comply with these requirements—for example, the absence of a water control program, a lack of periodic water testing, or the absence of monitoring of key parameters—can result in penalties, partial or total shutdown of the facility, and even criminal liability in the event of outbreaks affecting people.
Therefore, any water treatment and monitoring strategy for cooling towers and condensers must be explicitly designed to demonstrate regulatory compliance during health inspections and internal or external audits.
UNE Standards and Current Regulations in Spain Regarding Cooling Towers
The regulations applicable to cooling towers and evaporative condensers in Spain have undergone significant changes in recent years, with the primary objective of strengthening the prevention and control of Legionnaires’ disease and standardizing the technical criteria for design, maintenance, and sampling.
Royal Decree 487/2022, of June 21
Royal Decree 487/2022 establishes the health requirements for the prevention and control of legionellosis, repealing the previous Royal Decree 865/2003 effective January 2, 2023. Among its main changes compared to Royal Decree 865/2003 are the following:
- The former classification based on the probability of proliferation and spread has been eliminated, and the scope of application now covers any fixed or mobile facility in which Legionella is capable of proliferating and spreading. Within this framework, cooling towers and evaporative condensers are expressly included in Annex I as facilities for which it is mandatory to have a Legionella Prevention and Control Plan (PPCL) or, alternatively, a Legionella Health Plan (PSL).
- Owners of cooling towers and evaporative condensers are required to notify the regional health authority of the facility using the form in Annex II, within one month of the facility’s commissioning, specifying the number and technical characteristics of the facility, as well as any relevant modifications.
- A mandatory maintenance program is established which, for cooling towers and evaporative condensers, includes cleaning and disinfecting the entire system at least twice a year—preferably in early spring and early fall—and, in any case, every six months when the facility operates year-round, along with water treatment programs, sampling, and staff training.
- Corrective actions based on the count of Legionella spp.*, are detailed, with specific measures for ranges >100, >1,000, and >10,000 CFU/L, including resampling, review of the maintenance program, cleaning and disinfection, and verification of the biocide’s effectiveness.
In practice, this does not lower the requirements for cooling towers and evaporative condensers; on the contrary, because they are expressly listed in Annex I, they are subject to stricter requirements regarding design and location, water treatment, maintenance, periodic sampling, and reporting, regardless of any prior classification by risk level.
Royal Decree 614/2024, dated July 2
Royal Decree 614/2024 amends Royal Decree 487/2022, refining key aspects of its practical application. The main updates include:
- Revision of sampling frequencies and microbiological analysis, adapting control programs to the operational reality of the facilities.
- Clarification of the responsibilities of owners and operators in the implementation and updating of the PPCL and PSL, reinforcing the need for the plan to be a dynamic risk management tool rather than a purely formal document.
- Update of the notification and reporting templates for health authorities, in line with the new requirements and annexes of Royal Decree 487/2022.
In addition, Royal Decree 614/2024 sets a deadline for updating the plans:
The owners of the facilities referred to in Article 3.1 must update their PPCL or PSL to comply with the provisions of this Royal Decree by July 1, 2025.
This means that, as of that date, all cooling towers and evaporative condensers must have a PPCL or PSL that complies with the new regulatory framework.
UNE 100030 Standard
The UNE 100030 standard is the technical reference document for the prevention and control of the proliferation and spread of Legionella in systems that use water, produce aerosols, and may become sources of transmission during operation, service testing, or maintenance.
- The UNE 100030:2017 version replaced UNE 100030:2005 IN and updated criteria for design, maintenance, and microbiological control, in line with Royal Decree 865/2003, which was in effect at the time.
- In 2023, UNE 100030:2023 was published, which revokes and replaces the 2017 version and was explicitly designed to complement Royal Decree 487/2022 with detailed technical criteria. This 2023 version:
- Applies to all facilities that use water, generate aerosols, and may be susceptible to becoming a source of legionellosis, including cooling towers, evaporative condensers, and evaporative cooling equipment.
- It establishes facility design criteria to minimize stagnant water, facilitate cleaning, and reduce the formation of hazardous aerosols.
- It defines maintenance programs (cleaning frequency, disinfection, monitoring of physicochemical and microbiological parameters) and criteria for total aerobic counts (guideline values of <100,000 CFU/mL as a reference for evaluating the effectiveness of biocidal treatment).
- It includes corrective actions based on the count of Legionella spp.*, with action protocols covering adjustments to biocide levels, cleaning without shutdown, re-sampling after 15–30 days, and verification of effectiveness.
Future UNE 100030:2026 and the Evolution of the PPCL/PSL
The draft standard PNE 100030, “Prevention and Control of the Proliferation and Spread of Legionella in Facilities,” is currently undergoing public consultation. It is scheduled to be published as UNE 100030:2026 and will replace version 100030:2023.
This new text seeks to further complement Royal Decree 487/2022 and refine the practical application of the Legionella Prevention and Control Plans (PPCL) and the Legionella Health Plans (PSL)
According to the draft submitted for public comment and the analysis by UNE Working Group 12 (coordinated by Aqua España), the future UNE 100030:2026 aims to:
- Provide a more practical standard for action, especially regarding PPCLs and, above all, PSLs, ensuring that these plans serve as genuine risk management tools rather than merely bureaucratic documentation.
- To simplify and standardize documentation, prioritizing that the plans be strictly based on the principles of HACCP (Hazard Analysis and Critical Control Points) and WHO guidelines, to facilitate their implementation and auditing.
- Introduce a technical update by facility type, with specific adjustments to protocols for complex facilities that generate aerosols (potable water systems, cooling towers, misters, irrigation systems, etc.), with the goal of simultaneously optimizing performance and biosafety.
UNE 100030:2026 is expected to be published in the coming months, but until its final publication, UNE 100030:2023 remains the reference technical standard that complements Royal Decree 487/2022 and Royal Decree 614/2024, and upon which the PPCLs and PSLs for cooling towers and evaporative condensers must be based.
From Regulations to Practice: Water Control, Maintenance, and Cleaning in Cooling Towers
Based on this legal framework (Royal Decree 487/2022, Royal Decree 614/2024, and UNE 100030), the regulations themselves specify in detail what must be measured, how often, how the system should be designed, and when it is mandatory to clean and disinfect cooling towers and evaporative condensers.
These requirements are primarily specified in Annexes III, IV, and V of the royal decree.
Water Quality Limit Values for Cooling Towers
Annex III establishes the minimum water quality parameters that facilities covered by RD 487/2022 must meet. For cooling towers and evaporative condensers, the reference table specifies:
| Parameter | Required Value | Standard Details |
| Total Aerobes | ≤ 100,000 CFU/mL | Method of analysis: UNE-EN ISO 6222:1999 (colony count by plating on agar culture medium). |
| pH | Variable | Set based on the biocide and its optimal range of effectiveness. |
| Turbidity | < 15 UNF | If the system cannot maintain this value, it must be equipped with filtration systems in the water circuit. |
| Total iron | < 2 mg/L | Indicator associated with circuit corrosion and the carryover of metal oxides. |
| Conductivity | No fixed numerical value | Must be maintained within limits that, depending on the water’s composition (hardness, alkalinity, sulfates, etc.), prevent scaling and corrosion. |
| Temperature | No specific value for cooling towers | The table does not set a temperature limit for this type of facility, unlike for potable water systems |
Beyond the table, it is worth emphasizing two points:
- The turbidity limit (<15 UNF) is not just a “number to monitor”: when the system is unable to meet it, Annex III itself requires the incorporation of filtration into the water circuit.
- Conductivity is used as a control variable for the balance between scaling and corrosion, depending on the quality of the feedwater; in practice, it is the parameter that governs the blowdown schedule and the concentration cycle.
Minimum Monitoring Frequencies
Annex V, as amended by Royal Decree 614/2024, specifies the minimum frequency at which parameters must be monitored in cooling towers and evaporative condensers.
For these types of installations, Table 3 establishes:
| Parameter | Minimum Frequency | Remarks |
| Legionella spp. | Monthly | Strengthens monitoring compared to the standard quarterly practice under the previous framework |
| Total Aerobes | Quarterly | |
| pH | Daily | Depending on the biocide. On-site monitoring, preferably with continuous automatic readings. |
| Temperature | Daily | On-site monitoring, preferably with continuous automatic readings. |
| Turbidity | Weekly | On-site monitoring, preferably with continuous automatic readings. |
| Residual biocide | Daily | If applicable, with continuous automatic readings. When physical treatments are used, this is replaced by checks to ensure the disinfection system is functioning properly. |
| Total iron | Monthly | Monitoring for corrosion and oxides. |
| Conductivity | Monthly |
Furthermore, when samples are taken to test for Legionella spp., Article 14 requires that at a minimum, the following be determined on-site: pH (if the biocide is pH-dependent), temperature, conductivity, and, where applicable, residual disinfectant, so that the microbiological result is always interpreted within its physicochemical context.
These frequencies are legal minimums, not quality objectives; the health authority may increase them if it deems it necessary.
Design Parameters for Cooling Towers and Mandatory Equipment
Annex III itself sets forth a series of specific requirements regarding design, accessibility, and equipment for cooling towers and evaporative condensers.
These include:
- Location: They must be located in such a way as to minimize human exposure to aerosols, kept as far away as possible from occupied areas and from air conditioning or ventilation intakes of adjacent buildings.
- Accessibility: The facility and its components must allow for inspection, maintenance, cleaning, disinfection, sampling, and inspection without blind spots that hinder these operations.
- Sampling points: There must be accessible points for physicochemical and microbiological analyses and for measuring disinfectant levels, located as far as possible from the water supply and the biocide dosing point. In addition to the reservoir, there must be a sampling point in the return pipe; a device in the return circuit is recommended.
- Filtration systems: Mandatory in facilities that cannot maintain turbidity within the values established in the table, with filtration capacity sufficient to retain solids and sludge that feed the biofilm.
- Blowdown system: Must allow for complete draining of the facility and be automated based on the maximum permitted conductivity specified in the treatment program. Only upon technical justification may it be replaced by timers, rotameters, or other manually adjustable devices.
- High-efficiency droplet separator: Towers and condensers must be equipped with droplet separators whose water carryover is <0.002% of the circulating water flow rate, reducing aerosol emissions and, thereby, the risk of Legionella dispersion.
- Dosing systems: If biocides are used, it must be ensured that the system remains disinfected against Legionella at all times; where applicable, automatic dosing is required.
Annex IV adds a cross-cutting criterion: chemicals must be dosed preferably automatically, using systems with remote monitoring or control, supported by a program for periodic calibration of the instrumentation.
Cleaning and Disinfection: Schedule and Mandatory Situations
The water treatment program must include, with documented records, the procedures, products, dosages, precautions, and frequency for each cleaning and disinfection activity.
General Guidelines
In general, Royal Decree 487/2022 establishes that the inspection, cleaning, and disinfection of facilities must be performed at least once a year and, in addition, in the following cases:
- Initial startup of the facility.
- After a shutdown lasting more than one month (unless otherwise determined by the health authority).
- After a repair or structural modification.
- When a general inspection so recommends.
- When so determined by the health authority.
The regulation also notes that no disinfection will be effective unless preceded by a thorough cleaning, and that a minimum contact time for the disinfectant must be ensured, adjusting the pH when its effectiveness depends on it.
Specific to cooling towers and evaporative condensers
For cooling towers and evaporative condensers, Annex IV sets forth a stricter regime:
- The cleaning and disinfection of the entire system, including tanks if any, must be performed at least twice a year, preferably at the beginning of spring and fall—that is, every six months for non-seasonal facilities.
- The droplet separator, condenser, fill (if applicable), and water distribution system must be inspected every six months, and the basin, blowdown systems, treatment equipment, and dosing systems must be inspected monthly.
Part C of Annex IV also defines the step-by-step cleaning and disinfection procedure (preliminary steps, disinfection, mechanical cleaning, treatment of accessories, and follow-up steps), distinguishing between facilities that can suspend operations and those that must continue to operate.
What to do when Legionella spp. counts spike
Royal Decree 487/2022, as amended by Royal Decree 614/2024, establishes a table of corrective actions based on the count of Legionella spp. (CFU/L) in the water. The summary is as follows:
| Count of Legionella spp. | Actions to Be Taken |
| Not detected or <100 CFU/L | Continue with the current maintenance and monitoring programs without making any further changes. |
| ≥100 and <1,000 CFU/L | Review the maintenance schedule and water treatment protocol, make adjustments to reduce the concentration, and consider performing a cleaning and disinfection. Resample after 15–30 days following the implementation of these measures.
|
| ≥1,000 and <10,000 CFU/L | Review and revise the program, perform a thorough cleaning and disinfection of the facility, and take a new sample between 15 and 30 days later. If Legionella is not detected, a second sample is taken one month later; if either of the two samples remains positive, the programs must be reviewed and the necessary structural changes implemented. |
| ≥10.000 CFU/L | Shut down the facility and, if necessary, drain the system, clean and disinfect it before resuming service, and retest after 15–30 days. |
The final stage is not optional; it is an explicit requirement of the royal decree. When the test results are indeterminable, the circuit, the sampling procedure, and the maintenance program must be reviewed; cleaning and disinfection must be performed if necessary; and sampling must be repeated until valid results are obtained.
Installation notification and responsibilities
Beyond the technical obligations, the regulation establishes a clear framework for notification and responsibility.
- The owners of cooling towers and evaporative condensers must notify the regional health authority electronically using the form in Annex II, no later than one month after the facility becomes operational and also within one month of the permanent cessation of operations or of any significant modification.
- External service companies responsible for maintenance are required to request in writing from the owner proof of such notification and, if none exists, must notify the owner in writing, with a copy to the health authority.
Failure to comply with notification obligations and the concealment of technical data may be classified as a serious violation under health legislation, carrying significant financial penalties and, in the event of outbreaks affecting individuals, potential civil and criminal liability.
Regarding liability, the Royal Decree clarifies that it rests with the facility operator (owner or operator). When the facility is operated by an entity other than the owner, the operator shall assume liability, unless there is documentary evidence to the contrary; hence the importance of specifying this division of responsibility in the contract.
Records, traceability, and the role of continuous monitoring
Royal Decree 487/2022 requires that all programs (maintenance, water treatment, cleaning and disinfection, training, etc.) be supported by records detailing the actions taken, their results, any incidents, and the measures adopted, as well as the dates of shutdowns and restarts and the reasons for them.
These records must:
- Be stored preferably in digital format.
- Be signed via a sworn statement by the technical manager, the owner, or their representative.
- Be retained for at least five years from the date of creation and be available to the health authority in the event of an inspection.
When you add up daily pH, temperature, and biocide readings; weekly turbidity checks; automated conductivity-based purges; automatic dosing; monthly and quarterly analyses; and five years of historical data, the scenario outlined by the regulation is difficult to sustain with scattered manual records.
This is where continuous monitoring and data digitization cease to be an optional improvement and become the most reasonable way to comply with—and demonstrate compliance with—the requirements of Royal Decree 487/2022.
