Legionella Risk Management: 4 Steps and 10 Essential Elements for Effective Water Management Plans

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 your 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

Buildings are more than structures, they are ecosystems—and they require diligent maintenance to ensure the safety and comfort of their occupants. The cleanliness and safety of building water systems is an often neglected, but important task to protect human health. 

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 is 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. 

This guide emphasizes the necessity of comprehensive Water Management Plans (WMPs) and the role our Water Treatment experts play in helping you maintain these systems to prevent Legionella proliferation. 

Understanding ANSI/ASHRAE 188-2018

The ANSI/ASHRAE 188-2018 standard sets forth the foundational requirements for managing Legionella risks in building water systems. This, alongside resources such as “Control of Legionella in Mechanical Systems” by Public Works and Government Services Canada, provide a robust framework for developing and executing effective Water Management Plans (WMPs).  

These resources set minimum Legionella risk management requirements for new and existing building water systems. They identify the need for well-documented risk management processes and industry standards to prevent Legionella risks.

Why Do I Need a Water Management Plan?

A custom Water Management Plan is crucial for identifying Legionella growth risks and implementing control measures in building water systems, including cooling towers, spas, fountains, and potable water systems. This plan is not just a regulatory requirement but a roadmap to safeguard health.

Your WMP 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. 

4 Steps to Developing a Water Management Plan

Developing an ASHRAE 188 compliant WMP can significantly mitigate Legionella risks in hospitals, hotels, and commercial buildings. Essential steps include:

Four steps to develop a water management plan to prevent legionella.
  1. Describe the building’s water systems using text and flow diagrams
  2. Identify areas where Legionella could grow and spread 
  3. Establish and Monitor Control Measures and determine actions to take when measures are not effective
  4. Documenting and communicating all the activities related to Legionella control 

10 Essential Elements of a Good 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 Cooling Towers, Legionella and Water Management, read this article:

Enhancing Water Safety Through Partnership

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. 

Guardian Chemicals stands ready to support building owners in developing, executing, and maintaining effective Water Management Plans. By partnering with our experts, you ensure your building’s water systems are not just compliant but exemplify best practices in water safety and Legionella prevention.


Effective water system management in buildings is crucial for health and safety. With the right knowledge, commitment, and partnership, such as that offered by Guardian Chemicals, you can reduce and manage your Legionella risks.

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.

Table of Contents

FAQ: Legionella Risk Management in Building Water Systems

Navigating the complexities of Legionella prevention in building water systems can seem daunting, but armed with the right knowledge, you can create a safer environment for everyone inside. Whether you’re a facility manager, building owner, or concerned occupant, our FAQ provides information to help you manage Legionella risks. 

What is Legionella, and why is it a concern in building water systems?

Legionella is a type of bacteria that causes Legionnaires’ disease, a severe form of pneumonia, and Pontiac fever, a milder illness. It’s a concern in building water systems because it thrives in warm, stagnant water and can spread through aerosolized water droplets, posing significant health risks to occupants. 

What are the key components of a Water Management Plan (WMP) for Legionella?

A comprehensive WMP for Legionella includes assessing the building’s water system, identifying potential risk areas, implementing water treatment measures, setting temperature controls, developing cleaning protocols, monitoring water quality, training staff, and regularly reviewing and updating the plan.

How does the ANSI/ASHRAE 188-2018 standard relate to Legionella prevention?

The ANSI/ASHRAE 188-2018 standard provides minimum risk management requirements for building water systems to prevent Legionella growth. It outlines the need for documented processes and adherence to industry standards for effective Legionella risk management. 

Who should be involved in developing a Water Management Plan?

Developing a WMP should involve a multidisciplinary team, including facility management, engineering, maintenance staff, and water treatment professionals, such as those from Guardian Chemicals, to ensure a comprehensive and effective plan. 

What temperatures should be maintained to prevent Legionella growth?

To inhibit Legionella growth, maintain hot water temperatures at a minimum of 140°F (60°C) at the source and ensure it reaches at least 122°F (50°C) at points of use. Cold water should be kept below 68°F (20°C). 

How often should water systems be tested for Legionella?

Water systems should be tested for Legionella according to the frequency outlined in your WMP, which may vary based on system complexity, usage patterns, and previous test results. Consulting with water treatment experts like Guardian Chemicals can help determine the optimal testing frequency. 

Can Legionella be completely eliminated from water systems?

While it’s challenging to completely eradicate Legionella from all water systems, implementing a robust WMP and following best practices for water treatment can significantly reduce the risk of Legionella growth and spread.

What actions should be taken if Legionella is detected in a building water system?

If Legionella is detected, immediate actions include notifying local health authorities, isolating the affected areas, implementing remediation measures such as flushing and disinfecting the system, and communicating with building occupants about the risks and steps taken.

How can Guardian Chemicals assist in Legionella risk management?

Guardian Chemicals provides expert consultation, water treatment solutions, and support for developing and executing WMPs tailored to your building’s specific needs, helping ensure effective Legionella prevention and compliance with health and safety standards.

Why is ongoing review and updating of the Water Management Plan important?

Ongoing review and updating of the Water Management Plan are crucial to adapt to changes in building water systems, usage patterns, regulations, and advancements in water treatment technologies. These reviews help continuously reduce your Legionella risk.

Originally published June 9, 2023. Updated with additional content and FAQ April 5, 2024. 

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