Legionnaires’ disease is a very serious pneumonia (lung infection) caused by a bacteria called Legionella, which is found naturally in environments where water has become stagnant. The potential for Legionella contamination has grown as office rent rolls are down – particularly as some entire buildings have been vacant since the pandemic of 2019.

While disease outbreaks are more commonly associated with Health Care facilities, they aren’t specific to a particular industry, and they may occur at any place of business that has poorly maintained water systems. Common examples of building water systems where Legionella can grow and spread include:

  • Shower heads
  • Sink faucets
  • Cooling towers
  • Hot tubs
  • Decorative fountains
  • Water features
  • Hot water tanks and heaters
  • Large plumbing systems

Your workers and customers may be susceptible to Legionnaires’ if they inhale contaminated water droplets or respirable fine mists. To protect your business, staff and patrons, it’s important to understand how to prevent Legionella from entering your water systems. Ensuring good water quality is the first line of defense against Legionnaires’ disease. Specifically, effective maintenance and visual inspections can prevent sediment and water organism accumulation that promotes Legionella growth. The best way to accomplish this is through effective hazard assessment and prevention.

Hazard Assessments

When conducting hazard assessments, give extra attention to:

  • Locations in systems where water may stagnate (e.g., storage tanks, fountains or infrequently used faucets)
  • Hot water recirculation systems
  • Expansion tanks, hammer arrestors, bypass lines or other side-stream plumbing equipment where water may not flow regularly
  • Backflow prevention devices

Prevention Methods

In addition to performing hazard assessments, there are prevention methods business owners and property managers should consider.

  • Establish a team to proactively address Legionella issues at your workplace
  • Ensure cold-water systems are kept cold and hot water systems are regularly circulated to prevent stagnation. Domestic water heaters should be kept at 140° F. The American Society of Sanitary Engineering recommends that hot water tanks be set from 135° to 140°, to inhibit the growth of Legionella bacteria with the installation of anti-scald devices and tempering valves to prevent hot water injuries1
  • Flush all water systems regularly
  • Create written procedures for the proper operation and maintenance of water systems
  • Maintain records of water system inspections, cleanings and disinfections
  • Descale, clean and disinfect all water outlets regularly
  • Sample water from your systems regularly and maintain a record of test results. Use accredited labs when testing for bacteria
  • Check disinfectant and other chemical levels in hot tubs, water features and plumbing systems regularly. Clean these systems often and in accordance with the manufacturer’s instructions

Responding to an Outbreak

If Legionella is suspected or discovered at your workplace, you will need to find the source. To accomplish this, seek the expertise of environmental health and safety professionals and conduct a thorough building investigation. This will help you identify when, where and how people with suspected Legionnaires’ disease may have been exposed.

For more information on Legionnaires’ disease, consult our bulletins for general industries and for senior living communities.

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