COVID-19 Reopening Risk: Is There Legionella in Your Building's Water?

Stagnant water can be a breeding ground for waterborne pathogens, like legionella. Here's how to reduce the risk.


During this unprecedented COVID-19 pandemic, many families, workers, and students will remain at home both voluntarily and in accordance with state and local mandates. Many office, commercial, industrial, and educational facilities will remain minimally occupied, leading to lower water usage and stagnant water within a facility’s potable water system.


Because the building owner is responsible for the quality of water in a building’s potable water system – the water utility is only responsible for water quality up to the water meter – it is important that owners understand and manage the health risks associated with reduced water use.


Stagnant water poses several health risks, including growth of waterborne pathogens such as Legionella and Mycobacterium species, as well as increased potential for corrosion that results in release of lead from pipes and plumbing fixtures. Concerns regarding water quality and microbial regrowth generally arise when it takes more than two days for water to flow through a building water system. During the COVID-19 pandemic, many building water systems and entire commercial and business districts have experienced reduced water flows for five months or more.


As water ages in a building water system, the chlorine residual that was added by the water utility to limit microorganism growth dissipates. Without sufficient concentrations of chlorine, layers of microorganisms (biofilms) will form and grow inside the pipes and surfaces of the distribution system.


Particularly during warm conditions, stagnant water quickly reaches temperatures ideal for Legionella growth (77 – 108°F, 25-42°C). Over the past few decades, the number of Legionella outbreaks and deaths in the United States have increased. Legionella is a waterborne bacterium that can infect the lungs, causing Legionnaires disease and Pontiac fever. While other waterborne pathogens, such as Mycobacterium avium and Pseudomonas aeruginosa, can grow in stagnant water, most practices to address Legionella are protective for these other pathogens.


Addressing stagnant water concerns may seem daunting to building owners who have never had to consider these impacts before. An important first step to reopening a building (or maintaining safe operations in a building with reduced occupancy) is to develop a building water management plan that evaluates all the uses of water within the building and the potential health risks, including those from Legionella and lead. Water management plans help identify data gaps and better understand the sequence of actions needed prior to building reopening and during reduced occupancy. It is possible to develop a single water management plan for multiple buildings as long as any differences in construction, water usage, and occupancy are noted and evaluated.


Guidance on developing a building-specific water management plan is available on the Center for Disease Control (CDC) website. On May 29, 2020, American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) published Guideline 12-2020, “Managing the Risk of Legionella Associated with Building Water Systems,” to provide guidance on implementation of ANSI/ASHRAE Standard 188, Legionellosis: Risk Management for Building Water Systems. Key elements of the ASHRAE guidance include conducting a systematic analysis of the building water systems, identifying control measures and operational set points to limit microorganism growth, and identifying water quality and system monitoring and corrective actions.


Because the ASHRAE guidance was developed for all building types and is general in nature, it may be beneficial to obtain additional support from scientists and engineers who have specific experience and knowledge in maintaining water quality in potable water systems.Facility managers can provide support in a number of activities, including:

  • Evaluating the need for additional water system assessment based on water usage and occupancy;

  • Identifying high-risk locations and optimal cleaning strategies prior to reopening or for reduced occupancy conditions (e.g., HVAC systems, hot water re-circulation loops, decorative fountains, ice machines, etc.);

  • Determining when and how to conduct water quality testing;

  • Evaluating the benefits and risks of extensive building system-wide flushing based on monitoring results and building occupancy.


To avoid bringing stagnant water from water mains into the building, which may exacerbate water quality issues, it is important to check with the local water utility to confirm that the water mains in the neighborhood have experienced sufficient water usage, or if remedial measures such as flushing have been implemented. This is particularly important for buildings located in downtown cores, business parks, and campuses, where a substantial decrease in occupancy has occurred on a neighborhood-wide scale.


Once biofilms have grown and pathogens are present within a building water system, it can be extremely challenging to manage building water quality. Although extensive flushing may temporarily alleviate any microbial growth and public health concerns, continued reduced water use could facilitate future growth and problems could recur. Continued flushing during periods of low or intermittent water usage and water quality monitoring, including assessing chlorine residual and characterizing microorganisms, are key tools to understanding and maintaining building’s water system health.


If you need assistance in managing water quality and public health in your building's water systems, contact David Zeidner at 630-654-2550 or dzeidner@hygieneering.com to discuss your concerns and allow Hygieneering to assist in developing water management plans, sampling, and evaluating data.


This post was reproduced in its entirety from www.facilitiesnet.com. Dr. Sarahann Rackl is a Senior Manager of Chemical Regulation & Food Safety at Exponent. Dr. Alex Revchuk is an engineer in Environmental & Earth Sciences at Exponent. Dr. Erin Murphy is a Managing Scientist of Polymer Science & Materials Chemistry at Exponent at Exponent.

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