As we return to the workplace, it’s important to ask: How safe is your building’s water?
May 28, 2021
The formation of bacteria—and Legionnaires’ disease—can appear in stagnant water supplies, worsened from COVID-19. How can you prevent the spread?
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COVID-19 lockdowns have enforced a new normality many of us have never thought could occur in our lifetime. It’s now an everyday reality. Workplaces, schools, and heavily occupied buildings were forced to close for perhaps a year or more.
With a light at the end of the tunnel, some businesses have reopened their doors but may be unaware of the risks at play when reentering and using an idle building. One of the simplest hazards that can arise in an unused building are bacterial growths. These microbes can cause Legionnaires’ disease and are already raising concerns with reports in Birmingham, England; Montreal, Quebec; and Melbourne, Perth, and Sydney, Australia, to name some places where outbreaks have occurred.
How harmful are these bacteria growths? What preventable solutions are there to protect those returning to previously idle buildings?
Let’s break it down.
What is Legionnaires’ disease?
Legionnaires’ disease is a severe type of pneumonia caused by legionella bacteria. It causes swelling in the lungs. Adults over the age of 50 and people with weak immune systems, chronic lung disease, or heavy tobacco use are most at risk. Healthy people usually recover but often require hospitalization and antibiotics to treat the lung infection. About 1 in 10 die.
Legionnaires' disease doesn't spread from person to person. Instead, the bacteria spreads through mist, such as from air-conditioning units for large buildings. If a person inhales aerosol droplets containing the Legionnaires’ bacteria, it becomes dangerous.
How does it grow and where is it found?
When building water systems or cooling towers (air conditioning) aren’t running, bacteria can develop in the plumbing. It becomes a risk when water sits in pipes, even for just a few days. So, you can only imagine what can happen when water is stagnant for months. Biofilms are a combination of one or more forms of micro-organisms that grow on various surfaces. These microorganisms that formulate into biofilms include fungi, bacteria. and protists.
The legionella bacteria thrive in temperatures from 20-45˚C (68-113˚F). It can survive in systems below 20˚C but cannot reproduce.
It is found in air conditioning cooling towers, evaporative air conditioners, showers and hot water systems, or pools and hot tubs.
From a system design perspective, there are several ways to reduce the risk of legionella growth in the potable water system.
What can be done in hydraulic design to mitigate this risk?
As a hydraulics project engineer, I understand the complexities associated with creating a safe and reliable hydraulic system. Managing the risk of legionella growth needs to consider both system design and ongoing maintenance.
Any potable water system should be regularly flushed with running water. This will aid in clearing out bacterial maturation sitting in your pipes as the movement of water will assist in removing any biofilm.
It is crucial that when flushing out warm or hot water systems, to use of hot water over 60˚C, as this will control legionella. The disease grows most rapidly within 20-45˚C water, and so minimizing the opportunity for water within this temperature range is crucial.
From a system design perspective, there are several ways to reduce the risk of legionella growth in the potable water system. Ultraviolet filtration is one way to minimize legionella entering a system. UV should kill up to 99% of the bacteria.
To reduce the opportunity for biofilm to grow within the pipework, the design should minimize stagnant water. How do we do it? Limit the lengths of pipework used in a building, commonly referred to as a reduction of “dead leg”. What is a dead leg? It refers to a portion of pipework that directly feeds a sanitary fixture—and only has water flowing through it while the fixture is being used, creating opportunities for the water to become stagnant. The stagnant water allows for a higher risk of legionella growth, which can then spread to other areas of the system.
Through my experience in hydraulic services, I understand the needs to minimize the usage of dead leg to design more efficiently, particularly in hospitals and aged-care facilities. The implementation of a ring main assists in flushing and enabling the movement of water, which is crucial to reduce biofilm formations.
No matter how well designed a system is, regular maintenance to manage the risk of legionella growth is essential.
Building water systems—hidden but important
Buildings are complex, and their design requires the talents of multiple engineering disciplines. However, there is one system that is mostly invisible but indispensable for the health and safety of the occupants—hydraulic engineering. It is extraordinary to be a part in helping our communities thrive through water design solutions, particularly when we contribute to a hospital, school, or health facility.
Most of us are excited to return to public buildings after so long apart during the pandemic. As we reenter those facilities, it’s valuable to understand the challenges building owners face to keep everyone safe.