Preventing Legionella outbreaks in buildings like hotels

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Legionnaires’ disease is a very serious lung infection caused by the Legionella bacteria. It can potentially affect the water systems at hotels and resorts, and such outbreaks can be deadly and costly. Proper prevention measures can keep, occupants, guests and employees safe and healthy. It also makes good business sense.

Safety of occupants, tenants and guests is the top priority

  • Legionnaires’ disease is the cause of death for approximately ten per cent of the people who get it.
  • Outbreaks at hotels may interrupt services and operations. This can diminish the experience of guests and lead to significant financial costs and reputational issues.
  • Hotels are frequent settings for outbreaks.

Water management programs can prevent outbreaks

The underlying problems that lead to Legionnaires’ disease are totally preventable through water management programs. These water management programs are a continuous, multi-step process designed to:

  • Identify areas in the hotel building where Legionella could potentially grow and spread
  • Reduce risk by monitoring water systems
  • Take actions when risks are identified

Get started by creating an expert team with the adequate mix of skills so that you can develop an effective program.

Legionella can grow in different areas of hotels

Legionella can make your guests sick when the bacteria grow in water and then spread in droplets small enough for your guests and employees to breathe in. The bacteria grows best in warm or hot water that is not moving or that does not contain enough disinfectant to actually kill the bacteria.

  • Cooling towers: when disinfectant levels are too low, cooling tower fans may spray water infected with Legionella.
  • Showers: Legionella can potentially grow in and spread through showerheads if the water in our water system has low disinfectant levels.
  • Unoccupied Floors and rooms: low occupancy lowers water flow, which can eventually decrease disinfectant levels and hence increase the risk of Legionella growth.
  • Hot tubs: when hot tubs are not properly maintained, the warm temperature allows for growth of Legionella, which can later spread through water jets.
  • Water supply interruptions: events that cause the interruption of the delivery of municipal water to our hotel, such as a nearby construction, allow dirt to enter our system and use up disinfectant.
  • Fountains: Legionella may grow in warm areas of a fountain and therefore splashing can spread water containing Legionella.


Monitor the water quality parameters

The team in charge of managing the water management program should periodically monitor water quality parameters, such as temperature and disinfectant levels. By monitoring these parameters, your team can guarantee that the water systems are operating in a way that minimises hazardous conditions that could cause Legionella and other waterborne pathogens to grow.

If your control team finds that you are not meeting a parameter limit (e.g., temperature, disinfectant level), the next step will be to take the needed actions to get conditions back to within an acceptable parameter range. Examples of physical and chemical control limits to lower the risk of Legionella growth include:

  • Maintain hot water temperature at the highest temperature allowable by state codes and regulations
  • Make sure that disinfectant levels are detectable where water enters the hotel water system and at points of use
  • Measure the pH of your water to determine whether the disinfectant used in the hotel will be effective. Disinfectants work best within a narrow pH range


Pay close attention to trends and patters in your water parameter measurements. Where there are concerning trends or patters, examine and address the underlying issue. At times the solution to problems with water quality measurements might just be as simple as flushing low-use areas or perhaps simply adjusting the thermostat on the water heater.


Overview of WMPs or water management programs

Water management programs identify dangerous conditions and take actions to reduce the growth of Legionella as well as other waterborne pathogens in hotel water systems. Developing a water management program is a multi-step process that requires constant review. Such programs are an industry standard for large hotels in the United Kingdom.


Seven key elements

There are 7 key elements of a Legionella WMP or water management program:

  • Establish a qualified water management program team
  • Describe the hotel water systems using text and diagrams
  • Identify areas where Legionella could potentially grow
  • Decide where to apply control measures and how you will monitor them
  • Establish several ways to act and intervene when you cannot meet the control limits
  • Ensure the program is running as designed and that it is effective
  • Document and communicate all actions taken



Generally speaking, the principles of an effective water management should include:

  • Maintain water temperatures outside the ideal range for Legionella growth at all times
  • Prevent water stagnation
  • Guarantee an adequate disinfection
  • Maintain devices to prevent corrosion, biofilm growth and scale, all of which provide a habitat as well as nutrients for Legionella

Once established, WMPs or water management programs will need periodical monitoring of key areas for hazardous conditions and the use of certain responses to remediate such conditions when the assigned team detects them.

Corrective actions when the team finds Legionella

There is no known safe level of Legionella in hotel water systems. Different cases of Legionnaires’ disease are associated with extremely low levels of Legionella in hotel water systems. The intent of a WMP or water management program should be to manage hotel water systems. This, with the aim of lowering the hazardous conditions that let Legionella to grow and spread. In case the team decides to incorporate a Legionella risk assessment and regular environmental sampling for Legionella as part of the WMP, they need to decide how to respond if bacteria are found in the water systems.

The team needs to see if they actually find Legionella during regular environmental sampling (in the absence of disease). If so, it is advisable to explore possible reasons for this growth. Corrective actions, such as flushing the pipes or adjusting temperature levels, might be enough. Additional actions could be necessary if there are concerning trends, like for instance persistently positive samples at one specific location, positive samples in the main distribution point, positive samples in several points-of-use or diversity in the types of Legionella detected by the team.

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