Can Legionella Be Found in Drinking Water?
When people think about Legionella, one of the most common questions is whether the bacteria can be found in drinking water. The short answer is yes, Legionella can exist in water systems, including drinking water supplies. However, the presence of Legionella does not automatically mean that drinking the water will cause illness.
The main concern with Legionella is not simply the water itself, but the conditions that allow the bacteria to grow and the way people may be exposed. Understanding how Legionella behaves in water systems helps businesses, building owners, and facility managers take the right steps to reduce risk.
What Is Legionella?
Legionella is a type of bacteria that naturally exists in freshwater environments such as lakes, rivers, and streams. In small amounts, it is usually not considered a significant health concern.
Problems can occur when Legionella enters man-made water systems and finds suitable conditions to multiply. These conditions may include:
- Warm water temperatures
- Stagnant water
- Poor circulation
- Sediment buildup
- Inadequate maintenance
Once bacteria grow within a water system, certain activities that create fine water droplets can increase the possibility of exposure.
You can learn more about how Legionella develops through this guide on Legionella explained.
Can Legionella Be Present in Drinking Water?
Yes, Legionella can sometimes be detected in water systems used for drinking water. However, drinking contaminated water is not usually the main way people become infected.
Legionnaires’ disease most commonly occurs when someone inhales small droplets of water containing Legionella bacteria. These droplets may come from:
- Showers
- Taps that create spray
- Cooling systems
- Decorative water features
- Other aerosol-producing equipment
The Centers for Disease Control and Prevention (CDC) explains that people are generally exposed to Legionella by breathing in contaminated water droplets rather than by simply consuming water. (cdc.gov)
Does Drinking Water With Legionella Make You Sick?
For most people, swallowing water containing Legionella is not the typical cause of Legionnaires’ disease.
The main risk occurs when contaminated water enters the lungs through inhalation or when small droplets are accidentally aspirated into the respiratory system.
Certain individuals may have a higher risk of developing serious illness, including:
- Older adults
- People with weakened immune systems
- People with chronic lung conditions
- People who smoke
This is why water management is especially important in places such as healthcare facilities, hotels, and large residential buildings.
Where Can Legionella Enter Drinking Water Systems?
Legionella may enter building water systems from natural water sources and can become a concern when system conditions allow growth.
Potential areas include:
Hot Water Systems
Hot water storage tanks, pipes, and circulation systems can create favourable environments if temperatures are not properly controlled.
Plumbing Networks
Complex plumbing systems may contain areas where water moves slowly or becomes stagnant.
Storage Tanks
Poorly maintained storage tanks may allow sediment buildup and bacterial growth.
Low-Use Outlets
Unused bathrooms, guest rooms, or parts of buildings with reduced water use can experience increased risk.
More information about common risk locations is available in this resource on where Legionella can develop.
Why Drinking Water Systems Need Management
A common mistake is assuming that because water appears clean, it is automatically free from risk. Legionella cannot be identified by:
- Colour
- Smell
- Taste
- Appearance
This means businesses cannot rely only on visual checks. Effective prevention requires proper management of the entire water system.
A water management approach may include:
- Understanding plumbing design
- Monitoring temperatures
- Maintaining equipment
- Preventing stagnation
- Reviewing risks regularly
You can read more about safe building water practices in this overview of building water safety.
Can Boiling Water Remove Legionella?
Heating water can reduce or eliminate Legionella bacteria when temperatures and exposure times are sufficient. However, relying only on occasional heating is not a complete prevention strategy.
Businesses and building owners should focus on maintaining safe systems through:
- Regular inspections
- Proper temperature control
- Cleaning procedures
- Ongoing monitoring
A long-term prevention plan is more effective than reacting after a problem is discovered.
How Businesses Can Reduce Legionella Risks in Drinking Water Systems
Organisations responsible for buildings can take several practical steps.
1. Monitor Water Conditions
Regular checks help identify problems before they become serious.
2. Prevent Water Stagnation
Unused areas of plumbing should be managed to avoid prolonged periods of inactivity.
3. Maintain Equipment
Storage tanks, pumps, and plumbing components should be inspected and maintained.
4. Train Responsible Staff
Facilities teams should understand how water systems operate and what actions are required.
5. Keep Records
Documentation of maintenance, monitoring, and corrective actions supports effective water safety management.
Common Misconceptions About Legionella in Drinking Water
“All drinking water contains dangerous levels of Legionella”
This is incorrect. Legionella may exist in water environments, but risk depends on conditions that allow growth and exposure.
“If Legionella is detected, the building must close”
Not necessarily. The appropriate response depends on the situation, risk level, and professional assessment.
“Water filters completely remove Legionella risk”
Filtration may help in some situations, but it does not replace proper water system management.
Final Thoughts
Legionella can be found in drinking water systems, but the main health concern is usually exposure to contaminated water droplets rather than drinking the water itself.
For businesses and building owners, the best approach is prevention. Maintaining water systems, controlling risk factors, and following a structured management plan can help reduce the chances of Legionella growth.
For more information about Legionella prevention, testing, and common concerns, visit the FAQ or explore additional guidance through the blog.
