Mitigating Legionella Concerns in Vacant Buildings

The current COVID-19 pandemic has illuminated many weaknesses regarding how we design and construct water systems in our buildings. The most critical example is the rise in vacant buildings and the resulting potential for bacterial amplification. As water sits in piping systems, oxidizing disinfectants such as chlorine or chloramine dissipate.

Additionally, disinfectants such as chlorine or chloramine, depending on the concentration, will only inactivate 50 percent to 99 percent of waterborne pathogens. No disinfectant available is 100 percent effective; the best only gets to a 6-log reduction, or 99.9999 percent reduction of certain pathogens. This means less disinfectant is available to inactivate the bacteria, which can multiply and reproduce.

In response to this concern, a number of industry organizations and individuals have come out with guidance on how to mitigate or minimize the risk via good flushing and water treatment protocols. This culminated in the development of an International Association of Plumbing & Mechanical Officials/American Water Works Association document, “Responding to Water Stagnation in Buildings with Reduced or No Water Use: A Framework for Building Managers.”

The document goes a long way in giving more in-depth guidance and summarizing the available literature to building owners and plumbing engineers to help reduce the risk of waterborne-pathogen outbreaks due to building closure or reopening.

For engineers involved in plumbing system design, vacant buildings represent the latest iteration of a growing concern of Legionella and other waterborne pathogens in facilities. There are numerous competing considerations engineers need to balance during the design process. Some disinfectants cause corrosion. Higher temperatures can make water more aggressive. Redundancy of equipment or in pipe sizing creates more surfaces for biofilm and pathogens to grow. Owners don’t want to pay for unnecessary or extra equipment.

Additional Guidance on the Way

There are a multitude of concerns that engineers need to balance; coming up with good solutions would make this article into a book. Luckily, such information is on the way: the American Society of Plumbing Engineer’s Legionella Working Group is getting closer to releasing a guideline giving engineers much more directed guidance. I am hopeful that by mid-2021, the document will be available for public comment, if not released.

Additional documents are in the works to provide engineers with guidance. Others have already been released: The National Academies of Sciences, Engineering and Medicine’s “Consensus Report on Managing Legionella,” ASHRAE 514, ASHRAE 188 and ASHRAE Guideline 12, among others.

That being said, the process of flushing vacant buildings is worth further exploration. Facilities shut down during COVID-19 stay-at-home orders had the entire water industry screaming from the top of its lungs, “Flush the water systems!” I, too, joined the chorus and wrote and spoke about the issue on many occasions during 2020. But then I did ask myself the question: Don’t we have water often sitting unused for long periods during the construction process or when buildings are renovated?

I remembered a conversation with Molly Scanlon of the University of Arizona and Phigenics during 2019. She noted that we often have Infection Control Risk Assessment plans in hospitals for air, but what about the water? What are we doing to prevent the amplification of waterborne pathogens during construction? Since I didn’t have an answer at the time, I’ve continued to try to think of solutions to this conundrum — and so should you!

The COVID-19 crisis has shown us that good construction practice should include regular flushing of the water systems; now is an excellent time for engineers to add such language to their specifications. The typical industry practice (and, thus, specifications) is to hyper-chlorinate the piping between 50 and 200 parts/million for up to 24 hours before occupancy.

However, scientific literature has shown that biofilm can protect the bacteria from chlorine. Nor does scientific literature show that chlorine has the ability to remove the biofilm. Additionally, it is worth noting that biofilms start growing within 12 hours of building water being unused; in as little as several weeks, it can reach a significant mass. Waterborne pathogens, such as Legionella, can be introduced later into the system and inhabit the biofilm already formed. Therefore, it is important to have a flushing protocol during construction, but before occupancy, once water touches the piping systems.

Additionally, ensuring that contractors document these flushing procedures and test the water, at least for disinfectant and pathogens such as Legionella, is becoming increasingly important. Looking at turbidity of water and water hardness also may need to be considered. The IAPMO-AWWA document, which gives guidance for shutting down and reopening buildings, can be used by engineers to formulate directions to contractors during the construction process.

These kinds of flushing considerations can help mitigate the risk of a waterborne pathogen outbreak to future building occupants.

Flushing Can Be Automated

Additionally, with the advent of some incredibly innovative products on the market, flushing during construction can be automated. Electronically controlled or timer-controlled flushing valves can be placed at the end of a line and set to automatically flush water to a mop sink, floor sink or hub sink in high quantities.

Electronic faucet technology appears to be continually improving; wireless connectivity gives building owners the chance to remotely flush large quantities of fixtures simultaneously. Just be careful not to open all fixtures, as this could lead to siphonage!

Not only can the actions be automated, but many of these technologies, especially those connected electronically, include data-logging capabilities. In the world of Legionella litigation, it is worth remembering, “She/he who takes the best notes wins” in a court of law. The plumbing industry has responded to making this easier over the last several years with continuously more innovations.

In many ways, I predict that lawsuits over Legionella will drive the industry toward better documentation during the construction process of the water system. I picture a construction process for water systems that mirrors medical gas systems for certain building types. All installing contractors will need to obtain special certifications, a third party will need to inspect and confirm the installation process, and another third party will need to verify that the system is indeed safe via post-certification testing.

In medical gas systems, this entails the ASSE 6010, 6020 and 6030, respectively; for water systems in certain building types with Legionella concerns (such as hospitals, high-rises, etc.), this would look similar in many ways. Ensuring that all parties take the appropriate steps during the engineering and construction phases to avoid legal issues later will dictate it.

However, if engineers and contractors start planning for water safety during construction, it is likely too late in the process. From conversations I’ve had with legal experts such as Russ Nassof or Adam Green over the past several years, the Legionella risk mitigation process needs to start during the proposal phase.

Keep in mind that per ASHRAE 188, consultants such as consulting engineers may be included in a water management team. Do engineering consultant proposals include language to indicate that these services are included or excluded as part of base fees? Ambiguity in contracts is not a good thing. No one wants to provide services for free.

Additionally, if Consultant A is accounting for extra time to design for Legionella risk while Consultant B is not, how does the owner understand why Consultant A’s fees are higher than Consultant B’s? Being very clear during the proposal phase and thinking through which services need to be provided will likely lead to more success during the design process, construction phase, commissioning and beyond.

No More Engineering Generalists

I also predict we will see over the next several years an increase in specialization within engineering consulting. More firms will prioritize separating their HVAC and plumbing disciplines, and minimize the number of projects and staff where one engineer does both. The primary reason for this will be to avoid litigation due to mistakes on projects.

Peter Drucker, the founder of modern management and author of the book “On Management,” indicated this well almost 50 years ago: “A knowledge-based economy (that is an economy which is directly based on production, distribution and use of knowledge and information) requires knowledge-based workers … and that knowledge work is effective if only it is highly specialized (e.g., what makes a brain surgeon effective is that he is highly specialized in brain surgery, but by the same token couldn’t repair a damaged knee and would probably be helpless if confronted with a tropical parasite in the blood).

“This is true for all knowledge work. Generalists … are of limited use in a knowledge economy. In fact, they are productive only when they themselves become specialists in managing knowledge and knowledge workers. The knowledge needed in any activity has become highly specialized. It is therefore increasingly expensive and difficult to maintain enough critical mass for every major task in an enterprise. And because knowledge rapidly deteriorates unless it is used constantly, maintaining within an organization an activity that is used only intermittently guarantees incompetence.”

Firms that don’t push this specialization may put themselves at increased risk for lawsuits due to project mistakes. Plumbing expertise is continuing to diverge more and more from typical HVAC engineering knowledge. Understanding water chemistry/microbiology is one of the more recent developments, but systems such as medical gases have shown us for years that specialization is needed.

An argument could be made that these topics are why certifications such as ASSE 12080, ASSE 6020 (or 6005 or the upcoming ASSE medical gas design professional certification), and the ASPE CPD (Certified in Plumbing Design) should be required by any engineer who wants to design those systems. Time and time again in my career, I have seen a lack of knowledge by mechanical engineering generalists (or even HVAC engineering specialists who think they know the proper way to design plumbing systems) who place building occupants at risk.

No current National Council of Examiners for Engineering and Surveying professional engineer examination exists (let alone questions) that adequately tests engineers who design these systems. There is a strong case to be made that hospitals, hotels, universities, etc., should use additional certifications to ensure their engineers are qualified to design those systems. As our current crisis has shown us, public health and safety are at stake.

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