Articles & Resources by Vitralogy

May 15, 2020   •   3 minute read

How To Mitigate Legionella Growth During The COVID-19 Pandemic

Cooling tower set in a large building

Novel coronavirus (COVID-19) has affected every facet of life. With countless people sheltering in place and working remotely, this pandemic could, according to experts, cause another public health crisis as businesses begin to reopen: a potential explosion of Legionnaires’ disease, a severe and often lethal form of pneumonia caused by Legionella bacteria festering in underused and unoccupied buildings, and spread through aerosolized water droplets.

This affects plumbing, cooling towers, pools, hot tubs, decorative fountains, and any other systems connected to your building’s water supply, warn public health officials and agencies cited in a recent Reuters article titled “Buildings Closed by Coronavirus Face Another Risk: Legionnaires’ Disease.”

“The sudden and sweeping closures of schools, factories, businesses and government offices have created an unprecedented decline in water use,” it reads. “The lack of chlorinated water flowing through pipes, combined with irregular temperature changes, have created conditions ripe for the bacteria that causes Legionnaires’ disease.”

Commercial facilities “vacated or underutilized for more than three weeks is at risk for a Legionnaires’ outbreak, unless the water pipes are properly flushed and otherwise sanitized,” continues the piece.

As states around the country take steps toward reopening, it’s therefore critically important building managers take extra care to reduce Legionella’s risk and thwart its spread. Here’s how.



Increase routine maintenance and testing—while taking extra precautions.

While there are going to be far fewer, or zero people in your buildings for the foreseeable future, utilize COVID-19 and Legionella water system closure guidelines issued by the Centers for Disease Control and Prevention (CDC). Whoever is conducting testing and maintenance should wear a mask and gloves, wash their hands with soap and hot water frequently, and use alcohol-based hand sanitizer.

As for how to care for your water systems during the shutdown, continue to follow your water safety plan as written only if your building will be closed for a week or less. If closed for up to three weeks, flush your systems before reopening to the public.

Washington state was one of the first within the United States to be affected by COVID-19, and consequently developed and implemented useful measures to not only combat its spread, but also helpful guidance regarding preventing Legionella growth in anticipation of reopening businesses and government facilities.

Among those recommended by the Washington State Department of Health:

  • For any building closed for more than a month, increase routine monitoring of both your hot and cold systems.
  • Use an U.S. Environmental Protection Agency (EPA)-approved digital method for chlorine residual testing.
  • Test water entering the facility for temperature and chlorine residual daily.
  • Keep daily logs of all temperature and chlorine residual values.


Flush your water system to prevent stagnation and bacterial growth.

The aforementioned Reuters article states Canada’s Public Services and Procurement agency advised government offices that “pipes in any building that go more than one week with low or no occupancy should be thoroughly flushed for at least 30 minutes.”

In addition to the CDC and Washington state’s department of health, useful Legionella guidance has also been recently issued by the European Society for Clinical Microbiology and Infectious Diseases (ESGLI), including:

  • Flush cold water systems at least weekly.
  • For your hot water system, flush weekly and either monitor and maintain safe temperatures (above 120 degrees Fahrenheit or 49 degrees Celsius) at their distal fixtures or turn off the system, flush the hot water tank, refill with cold water, and practice cold water system maintenance. 
  • Clean and disinfect any decorative water features, such as fountains.
  • If you’re going to drain your system and it’s too big to be physically dried, perform a full system disinfection (to 50 ppm free chlorine for at least an hour) both before draining and again after refilling.


Even if you’re given the green light to reopen, do so slowly and implement a Legionella-specific water management plan.

The CDC recently updated its guidance for reopening buildings after a prolonged shutdown, publishing eight main protocols to minimize Legionella risk, along with direction on reducing mold, and advice for those with weakened immune systems. This includes:

  • Development of a Comprehensive Water Management Program
  • Proper Water Heater Maintenance & Temperature
  • Water System Flush
  • Decorative Water Features Cleaning
  • Hot Tub Safety
  • Cooling Tower Cleaning & Maintenance
  • Safety Equipment Cleaning & Maintenance
  • Water System Maintenance

As employees eventually return to your building and begin using the water system again, you need to be vigilant about mitigating the risk of Legionella—perhaps now more than ever.

That means stepping up your water management plan: perform daily temperature and chlorine residual tests, and weekly dip-slide inspections. As always, follow any federal, state, municipal or industry regulations, but keep in mind that we are living through unprecedented times which demand extra caution.


As always, using a digital solution will be the simplest and most cost-effective way to keep track of your more intense Legionella prevention plan, regardless of your industry. Vitralogy’s SmartCompliance is a high-tech, high-touch app that can help you track all the moving parts of your COVID-19-era water management plan. Contact us today to get started.


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