Tom Melhuish 8 min read

Legionella detection and prevention for businesses

Legionella is a type of pathogen that will grow in stagnant water systems at room temperature. Inhalation of Legionella bacteria can result in a severe form of pneumonia. Preventing and protecting your workforce and customers from exposure is critical for businesses.

In this guide, we will look at Legionella in detail, what it is, where it grows, and how to implement a prevention and detection program.

What is Legionella?

Legionella is a bacteria that causes a serious type of Pneumonia, called Legionnaires disease caused by the bacteria living in the water. People can become sick when inhaling the bacteria, which can grow in different systems using water within your premises – where water is stagnant for long periods of time.

For example the airconditioning unit. That’s why it’s important to have both a plan in place to detect Legionella, as well as preventing the bacteria.

Where can Legionella grow and spread?

It’s important as a business to understand where Legionella can grow and spread. Legionella can grow anywhere where water is held at room temperature for an extended period of time. Examples of common sources of Legionella are:

  • Tap flow restrictors
  • Showerheads*
  • Hoses
  • Pipes, valves, and fittings
  • Centrally-installed misters
  • Nonsteam aerosol-generating
  • Humidifiers*
  • Infrequently used equipment, including eyewash stations*
  • Ice machines*
  • Water heaters
  • Water-hammer arrestors
  • Expansion tanks
  • Water filters
  • Electronic and manual taps*
  • Aerators
  • Decorative fountains*
  • Cooling towers*
  • Medical devices* (such as CPAP machines, hydrotherapy equipment, bronchoscopes)
  • Hot and cold water storage tanks

*Note: The devices starred can also spread Legionella through aerosols or aspiration, making them even more high risk.

Factors that lead to Legionella Growth

Here we look at the internal and external factors that lead to Legionella growth. These are as follows:

Internal Factors

These are the internal factors that can lead to Legionella growth.

  • Fluctuating water temperature. This provides the perfect environment for Legionella to grow.
  • Water stagnation. Water stagnation reduces the temperature of the water and levels of disinfectant, therefore becoming the perfect place for Legionella to grow. Common causes that can contribute to water stagnation include building renovations that lead to reduced building occupancy – can occur in hotels etc., in the offseason.
  • The pH. The pH of the water (a measure of acidity) should sit between 6.5 and 8.5 where disinfectants are most effective.
  • Low levels of disinfectant. This will not kill off Legionella, or even inactivate Legionella at a low level. Even high-quality water entering a building can contain Legionella bacteria, so not having the correct disinfectant level can lead to growth within your water system.
  • Change in water pressure. This can cause biofilm to dislodge.
  • Scale. Scale soaks up the disinfectant used and creates a protected layer where Legionella can grow.
  • Biofilm. Protects Legionella from heat and disinfectant; provides food and shelter to germs; grows on any surface that is constantly moist and can last for decades.

External Factors

Here are the most common external factors that contribute to Legionella.

  • Breaks in the water main. Breaks in the water mains and changes in the water pressure can dislodge the biofilm and free Legionella bacteria into the water.
  • Construction work. Vibrations and changes in water pressure can dislodge biofilm and free Legionella into the water entering your building.
  • Changes in the water quality. A change in the water quality can lead to increased sediment and lower disinfectant levels, enabling Legionella bacteria. This is why monitoring the quality of your water is important.

How to test for Legionella

To test for Legionella, it’s best to call in a team of experts who will test in two ways, either using the swab method or the bottled method.

The swab sampling involves collecting a surface sample with a sterile swab. However, this isn’t frequently used as Legionella is also produced via aerosol or spray, which a swab test will not always detect.

The other method is to use the bottling of water. Bottle sampling consists of collecting water from potable water fixtures and also from warm water.

Bulk water sampling allows the quantification of the numbers of Legionella per specific volume of water.

This means it can trace Legionella bacteria in aerosols and spray.

Developing a Legionella water management program

A water management program is to help prevent the growth of Legionella on your premises; these are the steps you must undertake to get a full-proof Legionella water plan in place to prevent the growth and spread of the bacteria.

We recommend that companies implement a program with the help of external Legionella experts. Here are the key steps of establishing a water management program:

Establish a water management team

Consider who has the relevant knowledge of the water systems within the building and the correct personnel.

Skills and knowledge to consider whilst building your water management team are:

  • Knowledge of the water systems
  • Staff who can oversee the program
  • People who can identify and take corrective actions
  • Ability to monitor and document program performance
  • Knowledge of the water systems
  • Staff who can identify control locations and control limits
  • The ability to confirm program performance
  • The ability to communicate regularly about the program

Here are examples of the job roles that would be best suited to being part of the water management team:

  • Building owner
  • Building manager
  • Building administrator
  • Maintenance
  • Any engineering employees
  • Safety officers

What water system does your business use?

In this section of the water management program, you need to identify and note the water systems your business currently uses on their premises.

An example of these systems are as follows:

  • Coldwater distribution
  • Hot water distributed
  • Water entry pipes
  • Water heating systems
  • Hot, cold and wastewater discarding systems
  • Identify where it could grow on your premises
  • As part of your water management plan, you must identify key areas where Legionella may grow on your premises.

Make sure every floor level is considered, and any system that uses water has been listed.

Examples of where it could grow are:

  • Cooling tower
  • Sinks
  • Air conditioning units
  • Sprinkler systems
  • Evaporative cooling systems
  • Hot and cold water systems
  • Humidifiers
  • Air washers
  • Showers
  • Fountains

Decide where control measures for Legionella should be implemented.

You will need to decide where control measures for Legionella should be implemented. This is where you monitor a certain aspect, and if it exceeds those limits, it will notify the person overseeing the water management program.

Key control limits can be:

  • Water temperature
  • Disinfectant levels
  • Biofilm growth rate

You will need to identify the entry points to monitor the controls measures and who to notify when these are exceeded.

Establish ways to intervene if your control measures are not met

Once your control measures are agreed upon and everything is set to a standard you are comfortable with – it’s time to establish the process in which your control measures are not met.

This will be different per control measure as a drop in temperature will be managed to biofilm growth.

As long as you have your measures in place, they are being monitored by the correct people, and you have a response in place, this will help prevent growth.

Make sure your program runs smoothly.

Ensure you verify your plan. Before you begin, review the setup of your plan, and review if you’ve got the right people in place and the correct measures. If you have, then it’s time to monitor it over time.

Validate the plan regularly to ensure it’s working as expected and to improve certain processes. Always set time to review your plan, look at quarterly in the early stages, where you review the current setup and rectify any inefficient process and add in any other measures you think would improve the efficiency of your water management plan.

This could also include personnel; another staff member may be better suited or would add value as part of the water management team.

Document and communicate all activities

Finally, document and communicate all of your water management procedures. You need to have it all written down and documented for others to review.

The written program will need to include the following information:

  • Team members and their details.
  • Building information.
  • Water systems and descriptions of each system.
  • Your control measures.
  • Verification and validation process.
  • If testing is conducted, ensure you document all of the information, including the type of testing, transportation of the samples and lab it was sent to.

We hope this guide on Legionella detection and prevention was useful to you. Here are three more guides we think may be of interest to you:

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