Legionella Risk Management: The Critical Role of Water Management Plans in Building Systems

Do you know if you need a Water Management Plan to reduce your Legionella risk?

Are you aware of the best practices and components to develop a comprehensive Water Management Plan?

We’re here to help. In this article, we discuss best practices, components and the critical role of Water Management Plans to reduce Legionella risk in your building systems.

When maintaining your building systems, human health should always be a top priority. A major, yet often overlooked aspect, involves ensuring the safety and cleanliness of building water systems. Maintaining clean water systems starts with your Water Management Plan.

Prioritizing Human Health in Building Operations

Poorly maintained open cooling and potable water systems in buildings can pose significant health risks, especially when it comes to Legionellosis. Legionellosis refers to diseases caused by Legionella bacteria, which include Legionnaires’ disease—a severe form of pneumonia, and Pontiac fever—a milder flu-like illness. Legionellosis can be a significant threat to human health. 

Following proven risk reduction measures is the best way to manage the risk within your building. It starts with the development of a comprehensive Water Management Plan. However, you can’t prevent Legionellosis with a plan alone—you need proper execution, a good water treatment program, routine testing, and ongoing review. 

Understanding ANSI/ASHRAE 188-2018

The American National Standards Institute (ANSI) and the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) have published the ANSI/ASHRAE 188-2018 standard. This standard proposes the establishment of minimum Legionella risk management requirements for new and existing building water systems. It identifies the need for well-documented risk management processes and industry standards to prevent Legionella risks.

For additional information, you can also refer to Control of Legionella in Mechanical Systemsfrom Public Works and Government Services Canada (PWGSC). While this document is designed for federal buildings, it is a great resource for building owners, design professionals, and maintenance personnel. 

Why Do I Need a Water Management Plan?

A Water Management Plan provides clear guidelines on maintaining water systems to prevent the growth and spread of Legionella. It helps building and facility managers identify areas where Legionella can grow, set control limits, and establish corrective actions when control limits are not met.  

If you manage a building with water systems, such as: 

  • Open and closed cooling towers or evaporative condensers 
  • Whirlpools or spas 
  • Fountains 
  • Misters 
  • Atomizers 
  • Air washers 
  • Humidifiers 
  • Other non-potable water systems that release water aerosols 
  • Supplied hot domestic/potable water 

Then you need a Water Management Plan. 

Components of a Water Management Plan

An ASHRAE compliant Water Management Plan involves: 

  • Describing the building’s water systems using text and flow diagrams 
  • Identifying areas where Legionella could grow and spread 
  • Deciding where control measures should be applied and the limits to ensure they are effective 
  • Monitoring the effectiveness of the control measures 
  • Establishing steps to take when control measures are not effective 
  • Documenting and communicating all the activities related to Legionella control 

How to Develop a Water Management Plan

Developing a water management plan involves careful consideration of various factors. Your Water Management Plan should be a living, breathing document to guide your operations.  

Here are some steps to help you develop a water management plan: 

  1. Establish a Water Management Team: Designate a team responsible for developing and implementing the water management plan. This team should include representatives from facility management, engineering, maintenance, and water treatment professionals. 
  2. Understand the Building Water System: Conduct a thorough assessment of the building’s water system. Identify all water sources, including cooling towers, hot water tanks, showers, faucets, decorative fountains, and any other potential sources of Legionella growth. Document the system layout and plumbing schematics. 
  3. Identify Potential Risk Areas: Determine areas in the water system that may pose a risk for Legionella growth and transmission. These include stagnant water areas, dead legs, areas with inadequate temperature control, and places where water sprays, mists, or aerosols are present, such as showers and cooling towers. 
  4. Implement Water Treatment Measures: Establish a water treatment program to control Legionella growth. This may include disinfection methods, such as maintaining appropriate chlorine, disinfectant, or biocide levels. 
  5. Set Temperature Parameters: Establish temperature control measures to inhibit Legionella growth. Set hot water temperatures to at least 140°F (60°C) at the water heater and ensure a minimum temperature of 122°F (50°C) at the point of use. Cold water should be maintained below 68°F (20°C). 
  6. Develop Cleaning and Flushing Protocols: Define regular cleaning and flushing procedures for all water system components. This helps to remove sediment, biofilm, and potential Legionella sources. Develop a schedule and ensure adherence to these protocols. 
  7. Monitor Water Quality: Implement a water sampling and testing program to monitor the presence of Legionella bacteria. Identify appropriate sampling points and establish a frequency for testing. Your water treatment professional can assist. Ensure samples are sent to a qualified laboratory for analysis. 
  8. Establish Response Procedures: Develop procedures to respond to any detected Legionella contamination or Legionnaires’ disease cases. This includes notifying appropriate authorities, implementing remediation measures, and communicating with building occupants and stakeholders. 
  9. Train Personnel: Provide training to staff involved in operating and maintaining the building’s water system. Ensure they understand the water management plan, their responsibilities, and the importance of adhering to established protocols. 
  10. Regularly Review and Update the Plan: Periodically review and update the water management plan to incorporate any new equipment, processes, guidelines, regulations, or advancements in Legionella prevention practices. Stay informed about the latest recommendations from public health authorities. 


Water Management Plan development, execution, and reduction of Legionella risk is the responsibility of the building owner and designated employees on your Water Management Team. Guardian Chemicals can assist your Water Management Team with plan components for the building systems we provide chemistry for. 

By following these steps and maintaining a proactive approach, you can develop a robust building water management plan that effectively prevents Legionella outbreaks and ensures the safety of building occupants. 

If you would like to learn more about Legionella and Water Management, read this article:


Managing water systems in buildings is a challenging but crucial task. It requires knowledge, commitment, and the right partner to ensure all measures are appropriately implemented. 

When you are ready, we’re here to help you ensure your building remains a safe and healthy environment for all its occupants. A comprehensive water management plan combined with the right water treatment program and execution can help you prevent Legionella. 

Take the first step towards safeguarding your building’s water systems and contact us today.

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