Is Your Facility at Risk? Top 5 Legionella Danger Zones You May Be Overlooking

You’ve got a Water Management Plan. You’re doing the basics. So your building must be safe, right? Not necessarily. Many facility managers overlook hidden danger zones where Legionella can hide and multiply—areas that are easy to miss but just as risky.

Here are five high-risk zones you may not be monitoring closely enough:

1. Unused or Underused SpacesVacant wings, guest rooms, or seasonal facilities may go days or weeks without water flow, creating perfect conditions for stagnation and bacterial growth. Regular flushing and testing are a must.

2. Decorative Fountains and Water WallsThese features are visually appealing—but risky. Warm water and misting action create aerosolized droplets that can carry Legionella directly into airspace. If not cleaned and treated regularly, they become silent threats.

3. Ice Machines and Dental Water LinesYes, even ice machines. These systems can accumulate biofilm if not properly disinfected. In healthcare and dental environments, patients are especially vulnerable to waterborne bacteria.

4. Closed-Loop SystemsHeating and cooling loops may be “closed,” but they’re not immune to biofilm, scale, or microbial buildup. Poor maintenance can allow Legionella and other organisms to thrive unnoticed.

5. Neglected Water Storage TanksOut of sight, out of mind—but dangerous. Sediment buildup, temperature stratification, and lack of circulation make storage tanks a high-risk environment if not properly monitored and treated.

At Legionella Specialties, we conduct full system assessments to identify these risk zones and integrate them into your testing, treatment, and monitoring plans. You can’t manage what you don’t measure—and you shouldn’t assume your water is safe just because no one’s gotten sick yet.