Preventing Legionella

Preventing Legionella growth requires proper maintenance of water systems and devices that store or use water. Whether you are a homeowner, facility manager, or building owner, taking proactive steps can help reduce the risk of Legionella growth and transmission.

Home Maintenance

How does Legionella bacteria grow?

Homeowners can help reduce the risk of Legionella growth by maintaining water systems and devices that use water throughout the home.

Flush Infrequently Used Fixtures

Water that sits stagnant in plumbing systems can create conditions favorable for the growth of Legionella.

If faucets, showers, or other fixtures have not been used for an extended period, flush them weekly as outlined here:

Weekly Flushing Guidance

Run hot water for at least 5 minutes
Run cold water for at least 5 minutes
Flush all infrequently used fixtures, for example: guest bathrooms and outdoor faucets

Homeowners with private wells should consult their well service provider regarding additional maintenance and disinfection recommendations.

Maintain Water Heaters

Proper water heater maintenance can help prevent conditions that support Legionella growth.

Follow the manufacturer’s maintenance recommendations
Periodically inspect and service units as recommended
Ensure water heaters are functioning as designed

Clean and Maintain Devices with a Water Reservoir

Follow manufacturer recommendations for cleaning, disinfecting, and maintaining devices that store or use water, including:

Humidifiers
CPAP machines
Vaporizers
Water dispensers
Other devices with water reservoirs

Maintain Recreational and Decorative Water Features

Improperly maintained water features may support bacterial growth.

Examples include:

Hot tubs and spas
Decorative fountains
Misting systems

Follow manufacturer guidance for cleaning, maintenance, and water treatment.

Guidance for Facility Managers and Building Owners

Large or complex water systems require ongoing management to minimize the risk of Legionella growth.

Learn about Legionella

Ensure team members who work with the water system are knowledgeable about Legionella. Review free online training on Legionella prevention from the CDC here: Legionella Training | Control Legionella | CDC

Work with Qualified Professionals

Consider hiring a qualified water treatment professional, consultant, or engineer experienced in Legionella prevention and water management.

These professionals can assist with:

Building water system evaluations
Risk assessments
Development of water management programs (WMP)
Corrective actions and remediation strategies

Develop a Water Management Program (WMP)

A water management program (WMP) is a systematic approach for identifying and controlling conditions that may promote Legionella growth.

A comprehensive WMP should include these seven steps:

1. Establish a WMP team
  - Identify personnel responsible for implementing and maintaining the program.
2. Describe the building water systems
  - Document all water systems, their components, and how water flows through the facility.
3. Identify areas where Legionella could grow and spread
  - Identify areas where conditions may allow Legionella growth.
4. Decide where to apply and how to monitor control measures
  - Determine the best control points in your water systems and establish acceptable ranges for each.
5. Establish interventions when control limits aren’t met
  - Define corrective actions to take when monitoring shows that a control measure is outside its target range.
6. Make sure the program runs as designed and is effective
  - Verify often that procedures are being followed. Ensure that the program is reducing Legionella risk. This is often done through routine water sampling.
7. Document and communicate all the activities
  - Keep accurate records of monitoring results, corrective actions, and program reviews, and ensure relevant personnel are informed.

System-Specific Considerations

Cooling Towers

Cooling towers have been associated with Legionnaires’ disease outbreaks and require routine maintenance.

Recommended practices include:

Routine inspection and cleaning
Water treatment and disinfection
Monitoring of water quality parameters
Routine Legionella sampling
Maintaining maintenance and monitoring records

Potable Water Systems

Building water systems should be managed to reduce water stagnation. Key considerations include:

Address Dead Legs

Review water system and identify areas of low or no water flow, commonly called dead legs. Develop a plan to address these areas, such as targeted flushing, to prevent low or no water flow

Address Low-Occupancy Areas

Implement flushing protocols in areas with limited water use, including:

Vacant rooms
Seasonal facilities
Unoccupied building wings

Clean Fixtures

Regularly inspect and clean:

Faucet aerators
Showerheads
Other water fixtures that may accumulate biofilm

Decorative Water Features and Misting Systems

Decorative fountains, water features, and misting systems should be maintained according to established maintenance protocols outlined in a facility’s Water Management Program (WMP).

Recommended practices include:

Routine cleaning
Water treatment
Disinfectant monitoring
Inspection for biofilm accumulation
Water sampling
Maintaining maintenance and monitoring records

Construction, Remodeling, and Building Reopening

Construction activities and changes in building occupancy can increase the risk of Legionella growth.

Potential risk factors include:

Water main breaks
Prolonged water service interruptions
Plumbing modifications
Vibrations that dislodge biofilm within piping systems
Extended building shutdowns
Reopening buildings after periods of low occupancy

Facilities should evaluate and test their water systems following these events and implement flushing, disinfection, and/or other corrective measures as needed before returning systems to normal operation.

Contact Information

SNHD_EHoutbreaksupport@snhd.org
(702) 759-1504

Nevada Relay “Dial 711” (TTY)
After Hours & Public Health Emergencies
(702) 759-1000