Legionella in Buildings: What Property Managers and Engineers Need to Know

​A recent news story about Legionella detected in a federal building in Baltimore is a reminder that water system management is a critical responsibility for property managers and building engineers.

Legionella is a bacterium that can cause Legionnaires’ disease, a serious form of pneumonia, typically spread when people inhale tiny droplets of contaminated water from building systems.

While outbreaks often make headlines, the reality is that most Legionella risk is manageable with proper building operations and maintenance.

Here’s what CRE professionals should know.

Where Legionella Can Grow in Buildings

Legionella naturally occurs in water but can multiply in man-made building water systems, including:

• Cooling towers
• Domestic hot water systems
• Decorative fountains
• Ice machines
• Showers and plumbing fixtures
• Hot tubs or spas

The bacteria thrive in warm, stagnant water and biofilm buildup inside pipes or equipment.

How Property Managers Can Prevent Legionella

Prevention is primarily about good water system management.

Key practices include:

✔ Maintain proper water temperatures: Hot water should typically remain above ~140°F and cold water below ~68°F to inhibit growth.

✔ Maintain cooling towers properly: Scale control, corrosion control, and routine cleaning are essential to prevent bacterial growth.

✔ Implement a water management plan: Many facilities adopt a formal plan based on CDC/ASHRAE guidance.

✔ Prevent stagnant water: Unused fixtures, “dead legs” in piping, and idle equipment can create ideal conditions for bacteria.

✔ Use water treatment and biocides where appropriate: Chemical treatment programs are commonly used in cooling towers to control microbial growth.

✔ Inspect and clean systems regularly: Cooling towers should be cleaned and disinfected at least twice a year.

​How Buildings Should Check for Legionella

Routine monitoring includes:

• Periodic water sampling and lab testing
• Monitoring disinfectant levels
• Inspecting for sediment, scale, or biofilm
• Checking temperatures and system circulation

As a best practice, many organizations now conduct routine baseline testing to detect issues before they become a health risk.

What to Do If Legionella Is Detected

Detection does not automatically mean an outbreak, but it should trigger immediate action.

Typical response steps include:
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1. Notify building ownership and your water treatment vendor
2. Conduct additional testing to determine the scope of contamination
3. Perform system flushing and disinfection
4. Clean cooling towers or affected equipment
5. Increase monitoring until levels return to acceptable thresholds

In some cases, temporary measures such as point-of-use filters or fixture restrictions may be used while remediation occurs.

The Key Takeaway for CRE Professionals
​
Legionella management is an important part of building risk management, life safety, and operational best practices.

For property managers and building engineers, the priorities are simple:
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• Proactively maintain water systems
• Regularly monitor conditions
• Act quickly if contamination is detected

The good news: good maintenance practices are the best defense against a headline.

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