If someone told you your shower could make you sick, would you believe them?
Most of us assume the water running through our taps is safe, clean, treated, and reliable. But there’s a hidden risk that’s rarely talked about, and it’s sitting in pipes, tanks, and systems in both homes and offices. It doesn’t always make a grand entrance either. Sometimes, the effects are mistaken for a common cold, flu, or even pneumonia.
Let’s talk about Legionella.
This waterborne bacteria is more common than you’d think, and it can be dangerous under the right conditions. It thrives in warm, stagnant water. And when it’s inhaled through fine mist or vapor from the likes of showers, taps, hot tubs, and cooling systems, it can cause Legionnaires’ disease, a potentially serious form of pneumonia.
The reality is: this isn’t just a problem in hospitals or old buildings. Legionella has been found in everything from modern apartment blocks to office AC systems, and most people don’t even know it’s there.
What Is Legionella and Why Should You Care?
Legionella is a type of bacteria found in freshwater. It’s not usually a problem in nature because the bacteria are too diluted. But in man-made water systems — think tanks, pipes, heaters — it gets cosy, especially if the water isn’t moving much or is sitting at just the right temperature (between 77°F and 113°F).
That’s when Legionella can multiply.
Once it’s in the system, it doesn’t take much for it to become airborne. A shower, a spray tap, or even the mist from an air conditioning unit can release it into the air. If someone breathes in that mist? That’s when things can go wrong.
For healthy people, exposure might cause flu-like symptoms. For those who are older, have lung issues, or weakened immune systems, it can be far more serious.
And it’s not just the big outbreaks that are the issue. Small, undetected exposures can fly under the radar, causing illness that never gets linked back to the building’s water. If you haven’t had a legionella risk assessment, or don’t know if one has ever been done, that’s a potential blind spot worth addressing.
Common Places It Hides
The scary part is how many places are ideal for Legionella to grow. It doesn’t need a lot to thrive. And once it’s in a system, it can be hard to get rid of without proper handling.
Here are a few common culprits:
- Hot water tanks and heaters – If the temperature is too low, it’s a perfect breeding ground.
- Showers and faucets – Especially ones that aren’t used often, like guest bathrooms or office showers.
- Cooling towers and air conditioning systems – Especially large-scale units in office blocks or commercial buildings.
- Decorative fountains and water features – They look nice, but can release fine mist into the air.
- Spa pools, hot tubs, and whirlpools – Warm water plus bubbles equals airborne risk.
- Complex plumbing systems – The more dead ends or rarely used areas, the higher the chance of stagnation.
Even in homes, rarely used taps or outdoor hose lines can harbor bacteria if water is left sitting for long periods.
Why Homes and Offices Are Both at Risk
It’s easy to think this is something that only affects commercial buildings, but homes carry risk too. Water tanks, heaters, showers, and garden features all play a role. If you’ve got plumbing that doesn’t get regular use, like in a spare bathroom or a property that sits empty for weeks, that’s an opportunity for water to stagnate and bacteria to build.
In office buildings, things can be even more complicated. Many systems are larger, more complex, and harder to monitor. There may be areas that go unused for long periods, such as gym showers that rarely see activity or kitchen taps that only get used occasionally. Even air conditioning systems that recycle warm water can become an issue if they’re not maintained properly.
Extended periods of disuse, like during holidays or when people work remotely, only make the problem worse. If no one is flushing the systems or checking water temperatures, Legionella can thrive undisturbed.
How to Spot a Potential Problem
You won’t see Legionella floating around in your water, but there are some subtle warning signs that your system could be vulnerable.
If your water takes a long time to heat up or cool down, that’s a hint that your system may not be operating within the safe temperature range. In buildings where certain areas don’t get much water use, like infrequently used restrooms or taps in storage rooms, water can sit still and become a risk. Visible buildup around taps or showerheads, like scale, rust, or slime, can also point to conditions where bacteria thrive.
Sometimes the water might have a strange odor or taste, which could suggest bacterial growth. And then there’s the maintenance history. If no one seems to know when the system was last cleaned or checked, or if there’s no schedule in place for regular monitoring, it could be a ticking time bomb. In some cases, if people in the building have been experiencing pneumonia-like symptoms after using the facilities, it might be worth asking more questions.
What You Can Actually Do About It
You don’t need to be a water engineer to reduce the risk, but some basic actions can make a big difference:
- Keep hot water hot – Make sure your water heater is set to at least 140°F. Legionella dies off at higher temperatures
- Run your taps – Especially after periods of non-use. Flush water through showers, taps, and hose lines
- Clean your fixtures – Regularly descale and clean showerheads, taps, and any water outlets
- Check water systems regularly – Especially in offices or shared buildings, make sure systems are maintained
- Avoid dead legs – In plumbing, these are pipes with no water flow. They create pockets where bacteria thrive
- Keep cold water cold – Below 68°F is best to stop growth
And if you’re in charge of a building, whether it’s a small office or a large complex, bringing in a qualified professional to assess the system can give clarity. It’s not just about testing the water once. It’s about knowing where the risks are and making a plan to keep things safe long term.
A Problem You Can’t Afford to Ignore
Legionella doesn’t care if it’s a new building or an old one. It doesn’t care if the water looks clear. And it definitely doesn’t care if no one notices it for months.
But once someone gets sick, that changes fast.
The key is knowing that risk exists, even if you can’t see it. From homes to offices, regular checks, clean systems, and basic awareness can go a long way in preventing problems.
Water should be refreshing, not risky!
