Water Management Programs: Minimizing the Risk Associated with Legionella

Jul 31, 2017

Written by: Michael Groh, U.S. Water

Minimizing the risks associated with Legionella bacteria in building water systems can be challenging, and without the right expertise, it may put your facility at an increased risk for Legionella associated infections. In June of 2015, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standards Committee approved the final draft of Standard 188, Legionellosis: Risk Management for Building Water Systems. This document establishes the minimum requirements for the development, implementation, and ongoing maintenance of a Legionella risk management program in new and existing buildings. The Standard is a culmination of several years of work by experts in the fields of engineering, biology, and environmental health. The final version of Standard 188-2015 can be obtained from the ASHRAE website.

Shortly after ASHRAE 188 was published, a Legionella outbreak occurred in New York’s South Bronx area that infected 120 people and caused 12 deaths. The cause of the Legionella infection was traced to cooling towers in the immediate area. To prevent future outbreaks, New York City and the State of New York developed specific guidelines, which later became law, stating all cooling tower systems had to have a Water Management Program in place with documented quarterly inspections and testing.

In June of 2016 (amended June 2017), the Centers for Disease Control (CDC) reinforced the ASHRAE 188 guidance by publishing a toolkit entitled "Developing a Water Management Program to Reduce Legionella Growth and Spread in Buildings: A Practical Guide to Implementing Industry Standards." The purpose was to facilitate implementation of ASHRAE 188. The toolkit can be accessed on the CDC website.

With all the events occurring in the past two years, compliance to ASHRAE 188 through use of the CDC toolkit is necessary to keep water systems in buildings safe from Legionella.

About Legionella

Bacteria Occurrence
Legionella.jpgLegionella bacteria exist in the environment and undetectable amounts are in the water we drink every day. This typically poses no health problems unless large concentrations of the bacteria are aerosolized and inhaled deep into the lungs. The bacteria can concentrate in any water system, provided the right conditions exist: warm temperatures and/or the presence of algae or biofilm. HVAC cooling towers and evaporative condensers provide the potential concentration factors. Other dynamics for increased bacterial activity, which in extreme cases can lead to contracting Legionnaires’ Disease, include persons with depressed immune systems, smokers, elderly persons (65+), and organ transplant patients.

Cooling Tower Connection
Cooling towers remove excess heat from HVAC and process water systems; the medium for this heat transfer is water. Water is recirculated from the heat generating equipment (condensers) and allowed to cascade through a cooling tower; the process evaporates and cools the water. The cooled water returns to the condensers and the process repeats. Cooling towers are an ideal environment for bacteria like Legionella to grow and concentrate, and if steps are not taken to minimize growth, Legionella (and other bacteria) can amplify to dangerously high levels.

ASHRAE Standard 188-2015

The standard applies to human-occupied buildings excluding single family residential buildings. This standard is also intended for those involved in design, construction, installation, commissioning, operation, maintenance, and service of centralized building water systems and components.

Water systems included:
• Cooling towers or evaporative condensers
• Ornamental fountains
• Whirlpool spas
• Misters, air washer, humidifiers
• Devices that release water droplets

Buildings included:
• Buildings that have more than 10 stories
• Multiple housing units with a centralized hot water system
• Housing for occupants over the age of 65
• Buildings where patients stay over 24 hours
• Buildings where patients have a compromised immune system

It is important to note that this standard provides a framework and guidance only; the specifics of the Water Management Program are unique to each building and the different types of exposure hazards that exist. The standard does however call out specifics for documentation, responsible persons, and the different types of water systems that should be included in the program.

It is the responsibility of the building owner to develop a Water Management Program, utilizing ASHRAE 188, the CDC Toolkit, and CDC resources as guidance. If the building owner feels the need for professional help in developing the water management program, there are a number of third party independent consultants available to act as the primary developer of the water management program. The water treatment provider is often a critical member of the team, but should not be the primary developer of the plan due to internal conflicts of interest. The building owner should consider the following when developing their water management program:

• Develop a team of responsible individuals with knowledge of building water use and design. This team may include water treatment professionals or equipment manufacturers.

• Draw out and detail a water system flow schematic. This schematic does not need to be blueprint quality but should identify stagnation points (deadlegs), aerosolizing areas, water treatment equipment, etc. There should be two separate schematics – potable and non-potable.

• Develop operating procedures. This will include hazard control limits and control measures. This is one of the most important aspects of this standard and should be detailed carefully as control measures and the response to out of control limits will define the success or failure of the program.

Examples of control limits: monitoring free chlorine in hot and cold water, logging hot water temperatures, or establishing biocide use in a cooling tower.

Examples of control measures: using supplemental chlorine feed, flushing hot water tanks to prevent temperature stratification, or increasing biocide use for cooling towers in the summer months.

• Monitor and document all the critical points of the risk minimization plan. This should include corrective actions taken when measured values are outside of the control limits.

• Verify and validate the program is working as designed. The program effectiveness must be validated. Testing for Legionella is the most direct method for validation and is discussed in ASHRAE 188 as an option, but it is not required. Many building owners/managers conduct Legionella sampling as part of their program.

• Conduct and document compliance determination at least once per year and any time renovations, additions, or modifications are made to the building.

Additionally, when new construction or renovation is being considered, building design engineers and contractors have a responsibility to the building owner. They must provide documentation, schematics and instructions on monitoring and control systems, calibration procedures, and startup commissioning. They are also responsible for giving instructions on water system filling, disinfection, draining, design flow rates, volume capacities, design temperatures and balancing. Furthermore, contractors involved in disinfection of water systems must do so within three weeks of building occupancy.

Legionella bacteria are ubiquitous; it is estimated that close to 70% of plumbing systems harbor some level of the bacteria. Each year over 8,000 cases of Legionnaires’ Disease are diagnosed in the United States; it is estimated that 10 percent of those cases are fatal.

The development of a Water Management Program, which includes Legionella control strategies and risk minimization, may seem to be an overwhelming task, particularly for large buildings and centralized complex water systems. ASHRAE 188 and the CDC Toolkit are designed to make this program manageable. If help is deemed necessary, there are many qualified, independent professionals that can assist with working through the details of a program. The development and execution of a Water Management Program will help to protect your facility and keep building occupants safe from Legionella exposure.

Category: Industry Insights

Web Sponsors

Flynn Logo.pngStinson Services Minneapolis Commercial Roofing Contractors.png   2022 Website Logo - MN Roadways.png   identisys logo.png    Modern-Heating-and-Air.png