Legionella in Cyprus: Risks, Testing, Treatment & Prevention

What Is Legionella and Why Does It Matter in Cyprus?

Legionella is a group of bacteria found naturally in freshwater environments. The concern arises when the bacteria enter man-made water systems and find conditions that allow them to multiply. Water storage tanks, hot and cold water systems, pipework, taps and showers can all become relevant when water stagnates or other favourable conditions develop. Cyprus Public Health Services identifies water temperatures between 20°C and 45°C as particularly favourable for Legionella growth.

Legionella becomes a health risk when contaminated water is dispersed into small droplets or aerosols that can be inhaled or aspirated into the lungs. Showers are a common example, but other systems capable of producing aerosols can also create exposure. According to Cyprus Public Health Services, the infection is not considered to spread from person to person based on current scientific evidence.

Legionella and Legionnaires’ disease are not the same thing

These two terms are often used interchangeably, but they mean different things:

Why is Legionella relevant in Cyprus?

Legionella is particularly relevant to water-system management. Cyprus Public Health Services lists hot and cold water storage tanks, taps, showers, low-flow pipework, water heaters, sediment and biofilm among environments where Legionella can survive or multiply under favourable conditions. It also identifies hotels, hospitals and clinics, schools, universities and care facilities among premises where potentially relevant water systems may be present.

The Cyprus Department of Labour Inspection has also issued guidance highlighting the risk associated with stagnant water systems, including taps and showers, and recommends measures such as addressing stagnant water and sampling water systems where appropriate.

For homeowners and building managers in Nicosia, Limassol, Larnaca and elsewhere across Cyprus, the important point is not to assume that clear-looking water or a clean storage tank automatically means the entire water system is free from Legionella. Legionella cannot be confirmed or ruled out by visual inspection alone; appropriate water sampling and laboratory analysis are needed when its presence must be determined.

Where Does Legionella Grow in Water Systems?

Legionella can enter building water systems at low levels and multiply when conditions become favourable. The risk is influenced by several interacting factors, including water temperature, stagnation, water age, sediment, scale and biofilm. This means that the source of a Legionella problem may be a storage tank, but it may also be within the distribution pipework or at individual outlets.

For this reason, finding Legionella at a shower or tap does not automatically mean that the water storage tank is the source. The water system should be considered as a whole.

Water Storage Tanks

Water storage tanks can provide conditions favourable to Legionella when water remains stagnant for long periods or when sediment and biofilm accumulate.

The condition of the tank also matters. Poorly maintained covers, contamination entering the tank, accumulated sediment and insufficient water turnover can all reduce water hygiene.

Regular inspection and appropriate
water tank cleaning and disinfection
can therefore form an important part of water-system maintenance. However, cleaning the tank does not automatically disinfect downstream pipework, showers and other outlets.

Pipework and Stagnant Branches

Stagnation is one of the key conditions associated with Legionella growth. Water can remain in sections of pipework that are rarely used, oversized, isolated or no longer serving an actively used outlet.

• Rarely used bathrooms or guest rooms
• Unused taps and showers
• Redundant or poorly configured pipework
• Sections of a building that remain unoccupied
• Outlets with very low water use

Simply treating the storage tank may therefore fail to address contamination that is established farther downstream.

The
European Centre for Disease Prevention and Control
recommends regular flushing of taps and showers in unoccupied accommodation as part of Legionella risk reduction.

Showers, Taps and Low-Use Outlets

Showers are particularly relevant because they both contain water-system components where biofilm can develop and produce aerosols that can be inhaled.

Taps, showerheads, hoses and other outlets can also accumulate deposits and biofilm if they are not properly maintained.

Low-use outlets deserve particular attention. A shower that has not been used for an extended period can contain stagnant water even when the main storage tank is regularly replenished.

This is why Legionella prevention should consider the route water takes:

Storage → Distribution Pipework → Individual Outlet

rather than concentrating on only one component.

Temperature, Sediment and Biofilm

Temperature is another important factor. Cyprus Public Health Services identifies 20°C to 45°C as a favourable range for Legionella growth, while ECDC guidance recommends keeping cold water cold and hot water sufficiently hot as part of Legionella control.

Sediment and biofilm also matter. Biofilm is a layer of microorganisms and organic material that develops on wet internal surfaces, including inside pipes and tanks. It can provide an environment in which Legionella can persist and can make water-system control more difficult.

The combination of several conditions is therefore more important than any single factor:

Understanding where Legionella may be growing is important before deciding what corrective action is appropriate. If contamination is present within downstream pipework or outlets, treating only the storage tank may leave part of the problem unaddressed.

Can You Get Legionella from Showers or Drinking Water?

Legionella infection is mainly associated with breathing in small droplets of contaminated water or with contaminated water being aspirated into the lungs. This is why showers and other water systems that generate aerosols are particularly relevant when Legionella is present.

Simply drinking water containing Legionella is not considered the usual route of infection. However, aspiration can occur when water accidentally enters the lungs instead of travelling normally into the stomach, and some people are more vulnerable to infection than others.

Why Can Showers Be a Risk?

A shower produces a spray of very small water droplets. If Legionella has multiplied within the water system, contaminated droplets can become airborne around the person using the shower and may be inhaled.

The potential problem is not limited to the showerhead itself. Legionella may be associated with different parts of the system supplying it, including:

• The hot or cold water supply
• Water storage tanks
• Distribution pipework
• Flexible shower hoses
• Showerheads and other outlet components
• Sections of pipework where water has remained stagnant

This is also why an unused shower deserves attention. Water that remains stagnant in a branch of pipework for an extended period can create more favourable conditions for microbial growth, particularly when combined with suitable temperatures and biofilm.

The
European Centre for Disease Prevention and Control
recommends regular flushing of taps and showers in unoccupied tourist accommodation as one of its Legionella risk-reduction measures.

What About Drinking Water?

The distinction here is important:

Who Is More at Risk?

Not everyone exposed to Legionella develops Legionnaires’ disease. According to
Cyprus Public Health Services,
people at increased risk include older adults, smokers, people with chronic lung disease and people whose immune systems are weakened.

How Do You Know If Legionella Is in Your Water?

You cannot tell whether water contains Legionella simply by looking at it, smelling it or tasting it. Water may appear completely normal while Legionella is present somewhere within the water system. When its presence needs to be determined, appropriate samples must be collected and analysed microbiologically.

A Legionella investigation is also about where samples are taken, not just whether a single sample is positive or negative. Depending on the building and reason for testing, relevant sampling points may include storage tanks, hot and cold water systems, showers, taps and other selected outlets.

How Is Water Tested for Legionella?

One recognised laboratory method is ISO 11731:2017 — Water quality — Enumeration of Legionella. The standard specifies culture methods for isolating Legionella and estimating the number present in water samples. It applies to potable and other types of water, as well as water-related materials such as biofilm and sediment.

Laboratory reports commonly express culture results as CFU/L (colony-forming units per litre). The result should be interpreted together with factors such as the sampling point, type of water system and reason for testing rather than treated as an isolated number.

Can a Water Meter Detect Legionella?

No. Ordinary field meters and
water measuring tools
cannot tell you whether Legionella bacteria are present.

Several measurements can still be useful when investigating or managing a water system:

This means that a TDS meter, pH meter or chlorine/chlorine-dioxide measurement must not be presented as a Legionella test. Field measurements can support water-system assessment and treatment verification, but microbiological analysis is needed to determine the presence of culturable Legionella using the ISO 11731 approach.

What If You Already Have a Legionella Laboratory Result?

If you already have a laboratory report showing Legionella, keep the complete report, not just the positive number.

Useful information includes:

• The reported Legionella result and units
• The exact sampling location
• The date and time of sampling
• Whether the sample was from hot or cold water
• The laboratory method used
• Any additional information provided by the laboratory

A positive result from a storage tank and a positive result from a particular shower or tap can point to different questions about the water system. Understanding where the sample came from helps determine what should be investigated next.

What If You Need Legionella Testing?

If you suspect a problem but do not yet have a laboratory result, appropriate microbiological testing is the correct way to determine whether Legionella is present.

Contact WaterFilterNet
to discuss appropriate laboratory testing options. We will not substitute ordinary water-quality measurements for microbiological Legionella analysis.

What Should You Do If Legionella Is Found?

A positive Legionella result should be taken seriously, but the correct response depends on where the sample was taken, the level reported and the design and condition of the water system. Treatment should therefore begin with understanding the result and the affected system rather than automatically adding disinfectant to a water tank.

A positive sample from a storage tank, for example, presents a different investigation from a positive shower or tap when tank samples are negative. The objective is to identify where conditions are allowing Legionella to persist or multiply and then apply appropriate corrective measures.

1. Review the Laboratory Result

Start with the complete laboratory report.

Important information includes:

• Legionella concentration and units, usually CFU/L
• Sampling location
• Sample date
• Hot or cold water
• Laboratory method
• Any species or serogroup information reported
• Results from other sampling points in the same building

Multiple results can be particularly useful because their pattern across the water system may help determine where further investigation is needed.

A single number should not be interpreted without knowing where and how the sample was collected.

2. Assess the Affected Water System

The next step is to understand the system supplying the positive sampling point.

Depending on the building, this may involve examining:

• Water storage tanks
• Hot and cold water distribution
• Pipework configuration
• Low-use or stagnant branches
• Showers and taps
• Sediment and visible contamination
• Temperature
• Disinfectant residual where relevant
• Recent periods of low occupancy or non-use

The aim is not simply to find something that can be disinfected. It is to understand why favourable conditions may have developed and which parts of the system require attention.

3. Choose Corrective Actions for the Actual Problem

There is no single corrective action that is appropriate for every Legionella result.

Depending on the findings, remedial measures may include:

There is no universal Legionella treatment for every building. Established water-management guidance recognises measures such as cleaning, temperature control and disinfection, but the appropriate intervention depends on the water system and the conditions identified.

This is why tank cleaning alone should not automatically be described as Legionella treatment for an entire building. Where the tank itself requires attention, professional
water tank cleaning and disinfection
may form part of the corrective work, but downstream pipework and outlets may require separate measures.

4. Verify That the Corrective Action Worked

Completing a disinfection procedure is not the same as proving that Legionella has been controlled.

Field measurements such as temperature, pH or disinfectant residual can help confirm that treatment conditions were achieved. However, they do not detect Legionella.

Where microbiological verification is appropriate, follow-up laboratory sampling can provide evidence about whether the corrective measures have been effective.

5. Reduce the Conditions That Allowed the Problem to Develop

A successful response should also consider why the problem occurred.

If stagnation, poor water turnover, sediment, unsuitable temperatures, neglected outlets or another system condition contributed to the problem, disinfection without addressing those conditions may leave an opportunity for the problem to recur.

For larger or more complex buildings, ongoing water-system management may therefore be required rather than relying only on one-off corrective treatment.

Technical reference:
CDC — Steps to Develop a Water Management Program ↗

Legionella Prevention in Cyprus — Frequently Asked Questions

Legionella prevention depends on managing the conditions that allow the bacteria to multiply within a water system. There is no single filter, chemical or one-off cleaning procedure that can guarantee a building will remain free from Legionella.

Good water-system management focuses on temperature, water movement, cleanliness, maintenance and identifying areas where water can stagnate.

For homes and buildings in Cyprus, practical measures may include:

The
European Centre for Disease Prevention and Control
advises measures including maintaining appropriate hot and cold water temperatures, regularly flushing unused outlets and keeping water-system components clean. The exact control measures required depend on the building and water system.

Legionella Prevention in Cyprus Workplaces and Hotels

Legionella is not only a residential water issue. Larger and more complex water systems can require more structured management because they may contain extensive pipework, multiple storage points and outlets with different usage patterns.

On 8 July 2026, the Cyprus Department of Labour Inspection issued a specific announcement concerning the prevention and control of Legionella in workplaces and hotel establishments, highlighting the importance of appropriate preventive and control measures.

For employers and building operators, Legionella should therefore be considered as part of appropriate water-system and occupational safety management where the risk is relevant.

Official Cyprus information:
Department of Labour Inspection — Legionella Prevention and Control ↗