Legionnaires’ Disease Prevention for Building Water Systems

Legionnaires’ disease prevention starts with effective building water system management. The disease is a serious type of pneumonia caused by Legionella bacteria. People can become infected when they breathe in mist that contains the bacteria, often from building water systems or devices that create water droplets.

For building owners and managers, the goal is to reduce conditions that allow Legionella to grow and spread. A practical approach combines a building-specific water management program, routine maintenance, monitoring and documented corrective action.

What is Legionnaires’ Disease?

Legionnaires’ disease is a severe form of pneumonia caused by Legionella bacteria. Legionella can also cause Pontiac fever, a milder illness that does not involve pneumonia. Symptoms of Legionnaires’ disease typically develop two to 14 days after exposure, although they can take longer to appear.

Certain people face a higher risk of illness, including adults age 50 or older, current or former smokers and people with chronic lung disease or weakened immune systems. The Centers for Disease Control and Prevention (CDC) reports that about one in 10 people who become ill with Legionnaires’ disease die from complications.

How is Legionnaires’ Disease Contracted?

People generally contract Legionnaires’ disease by breathing in small water droplets or mist that contain Legionella bacteria. In general, the disease is not spread from person to person. Potential exposure sources can include showers, faucets, cooling towers, hot tubs and spas, decorative fountains and other devices that aerosolize water.

Where Can Legionella Grow in Building Water Systems?

Legionella can grow when building water systems create favorable conditions. Risk can increase where water becomes stagnant, temperatures support bacterial growth or sediment, scale, corrosion and biofilm provide habitat and nutrients.

• Hot- and cold-water systems, including water heaters and storage tanks
• Pipes with little or no water flow, including lines serving unoccupied rooms
• Dead legs and other sections of pipe where water can stagnate
• Cooling towers and evaporative condensers
• Hot tubs, whirlpools and spas
• Decorative fountains and other water features
• Showerheads, faucets, hoses, seals and other components where scale or biofilm can develop

How Can Businesses Support Legionnaires’ Disease Prevention?

A Legionella water management program can help an organization identify hazardous conditions and define how it will control, monitor and respond to them. The program should be tailored to the building, its water systems, its devices and the people who use the facility.

Build a water management team

Assign qualified people to oversee the program. Define responsibilities for maintenance, monitoring, documentation, corrective action and communication. A consultant with Legionella-specific environmental expertise may be helpful for complex systems or higher-risk facilities.

Describe the building water systems

Create an accurate description of how water enters, moves through and leaves the building. Include hot- and cold-water systems and devices that may create aerosols, such as cooling towers, hot tubs and decorative fountains.

Identify areas where Legionella could grow and spread

Evaluate areas with low flow, stagnation, sediment, scale, corrosion, biofilm or temperatures that may support bacterial growth. Consider occupancy patterns, seasonal shutdowns, renovations and changes in water use.

Establish and monitor control measures

Define control measures appropriate for the facility and identify how they will be monitored. Examples may include maintaining water temperatures, supporting adequate disinfection, preventing stagnation and maintaining devices to limit sediment, scale, corrosion and biofilm. Follow applicable codes, regulations, manufacturer instructions and professional guidance.

Respond when control limits are not met

Document corrective actions in advance so staff know what to do when monitoring identifies a problem. Response steps should match the facility, system and level of risk and may require qualified technical or public health support.

Verify, document and improve the program

Confirm that the program is operating as designed and that control measures are effective. Keep records of monitoring, maintenance, corrective actions and program reviews. Update the program when building conditions, equipment or occupancy change.

Building Systems and Devices That May Need Added Attention

• Cooling towers and evaporative condensers
• Hot tubs, whirlpools and spas
• Decorative fountains and indoor water features
• Showers and faucets in low-use or unoccupied areas
• Water heaters and storage tanks
• Large or complex plumbing systems
• Buildings that house or serve people at increased risk

Why Stagnant Water is a Legionella Risk

Low water use can reduce disinfectant levels and create conditions that support biofilm. Unoccupied rooms, seasonal buildings and equipment shutdowns can therefore require additional planning. Review flushing, maintenance and recommissioning practices as part of the water management program and applicable professional guidance.

Legionnaires’ Disease Prevention: Key Takeaways

• Use a building-specific Legionella water management program.
• Identify systems and devices where Legionella could grow or spread.
• Monitor defined control measures and respond when limits are not met.
• Reduce stagnation and maintain systems to limit sediment, scale, corrosion and biofilm.
• Document activities and review the program when conditions change.

Consistent water management can help reduce the risk of Legionella growth and exposure. Building owners and managers should coordinate with qualified professionals and follow applicable public health guidance, codes, regulations and manufacturer requirements.

Frequently Asked Questions (FAQ)

Sources

• Centers for Disease Control and Prevention, “About Legionnaires’ Disease,”
• Centers for Disease Control and Prevention (CDC). "Legionella."