The new government, scientific, and industry publications on COVID-19 and building water systems (see “Further Reading” below)—hundreds of pages counting the papers referenced in them—boil down to four key warnings:
1. Prevent viruses, gases, and other airborne contaminants from entering the building through drains or drainage systems.
In its March 3, 2020, technical brief on COVID-19, the World Health Organization (WHO) cited concerns that a faulty wastewater drainage system may have contributed to the transmission of the COVID-19 virus in a high-rise apartment building in Wuhan, China (WHO 2020).
WHO investigators found similar drainage system conditions in the spread of the SARS (Severe Acute Respiratory Syndrome) coronavirus in a high-rise apartment building in Hong Kong in 2003, implicating dry floor drain trap seals in the airborne transmission of the virus between apartment units (Yu ITS 2004). Cases were attributed to contaminated droplets transmitted from ill persons via a waste stack to bathrooms in other apartment units after being sucked in through floor drains with dry traps, particularly when the bathroom fan was running (WHO 2006).
Pete DeMarco of the International Association of Plumbing and Mechanical Officials (IAPMO) opined that transmission of the COVID-19 virus through drainage systems of buildings designed and constructed in compliance with the US and similar plumbing codes is possible but unlikely (DeMarco 2020).
However, in correspondence published in The Lancet, researchers at Heriot-Watt University’s Institute for Sustainable Building Design warned the “potential for a substantial viral load within the wastewater plumbing system (and therefore the main sewer system), in combination with the potential for airborne transmission due to aerosolization of the virus, calls for wastewater plumbing systems to be considered as a potential transmission pathway for COVID-19” (Gormley 2020).
Gormley and Aspray pointed out that although self-isolation can reduce direct person-to-person transmission, it could actually increase the spread of the virus via drainage systems: “High concentrations of infected people contribute to a higher viral load in the system, thus leading to a higher risk of disease spread. Self-isolation can lead to a greater number of infected people in a building and potential system overuse.”
Although more research is needed on the potential for virus transmission via drainage systems and risk factors for it, the 2003 Hong Kong and 2019 Wuhan investigations certainly highlight the need to ensure drainage systems are designed and maintained per codes and best practices.
2. Minimize stagnation in buildings while closed or partially occupied.
Buildings shut down or occupied less than normal become more prone to Legionella and other pathogens due to stagnation.
Stagnation will not be a problem in buildings that have kept up with their water management program (WMP) because a comprehensive WMP per ASHRAE Standard 188 will include specific measures for minimizing stagnation even during periods of low use. Unfortunately, even though the CDC has strongly recommended WMPs since 2016, only a small percentage of buildings have one. In its COVID-19 guidance, the CDC again instructed building owners to “Develop a comprehensive water management program (WMP) for your water system and all devices that use water,” but it’s too late to prevent stagnation that has developed over the past two months, and the cost of remediation could be high.
3. Flush domestic water (potable) plumbing systems prior to re-opening closed buildings.
Government agencies, industry associations, universities, and even attorneys have issued warnings to flush COVID-closed buildings prior to reopening them, and some have provided instructions for flushing procedures.
The optimum flushing frequency and flush times will vary from building to building depending on multiple factors including system layout, pipe lengths and sizes, water quality, fixture types, and usage. Proctor’s paper gives an excellent overview of flushing procedures, with references to studies.
Bear in mind that flushing will not solve a Legionella problem, even if performed properly.
4. Start up idled equipment per applicable regulations and best practices.
Any equipment that has been shut down—such as cooling towers, direct evaporative air coolers, decorative fountains, water-based humidifiers, misting systems, pools and spas—should be restarted per ASHRAE (ASHRAE 2020) recommendations for reducing the risk of Legionella and other pathogens.
Below are documents for further reading.
This article was adapted from LAMPS training note 4.107, “Coronavirus (COVID-19) and Water Management Plans.” LAMPS WMP users should review 4.107 and implement the control measures listed in it.
Please comment below. What other measures would you recommend to building owners?
Further Reading
CDC. 2020. Guidance for Building Water Systems. Centers for Disease Control and Prevention.
CDC. 2020. Water Transmission and COVID-19. Centers for Disease Control and Prevention.
Demarco P. 2020. Rehabilitating Stagnant Building Water Systems – A Timely Reminder from the IAPMO Group.
George R. 2020. Press Release: Flushing Bacteria from Stagnant Building Water Piping. Monroe, MI: Plumb-Tech Design & Consulting Services LLC. April 22, 2020.
IAPMO 2017. Uniform Codes Spotlight. International Association of Plumbing and Mechanical Officials.
LAMPS Training 4.030 Testing Water Supply Disinfectant Levels
LAMPS Training 4.031 Flushing Domestic Water Points of Use (POUs) Routinely
LAMPS Training 4.037 Domestic Water Disinfection Prior to Occupancy of New or Renovated Buildings
LAMPS Training 4.039 Domestic Water Disinfection: Temporary (Emergency) Procedures
LAMPS Training 4.093 Domestic Water: Managing Temporary Total or Partial System Shutdowns
LAMPS Training 4.107 COVID-19 Coronavirus and WMPs
LAMPS Training 4.108 Drainage Systems
LAMPS Training 4.109 Drain Trap Maintenance
Purdue University, Center for Plumbing Safety. Flushing Plans.
WADOH. 2020. COVID-19 Guidance for Legionella and Building Water System Closures. Washington State Department of Health. April 14, 2020.
WHO. 2006. Health Aspects of Plumbing. Geneva: World Health Organization.
Hello,
And today as a method of contact tracing city departments of health are tracing potential outbreaks of COVID-19 in the sewer systems all the way to the buildings that it originated from. It’s time to test and treat the influent of the waste stream into the waste water treatment facilities as well.
I hadn’t read about that, Mike. Thanks for sharing!
Matt you can find more about sewershed monitoring and contact-tracing by reviewing some of my posts on LinkedIn at the following hashtags
#COVID19 #WBE #EPIAPP #DETER #DTRT
Thanks Michael!
Thanks Matt! The fecal route was confirmed in Wuhan apartment complex with sub par plumbing. A LOT of traps have dried out while our buildings have stood idle. If we don’t bring these buildings back with consideration of drains as a vector we could compound the problem. This article is a must for facility engineers bringing back unused or little used spaces.
Good point, Pat. There have been so many warnings about flushing buildings to reduce Legionella risk but not much about checking for dry traps. We added a control measure to LAMPS for that and notified all our WMP users. Thanks for commenting
Confirmed is an awfully strong word. I don’t believe that it has been confirmed but rather suggested as a possible and perhaps even probable route.
I would have to once again review the study.
Great article, Matt, a good distillation of available resources, which can get confusing! I would recommend, as have many states, to test for common water quality parameters if the building has been closed or partially closed. Testing I have seen recommended include: disinfectant residual, temperature of water, turbidity, and L pneumophila. CDC has made a strong connection between closed buildings and Legionnaires’ disease risk. As you well stated, having a WMP reduces that risk; I hope others now adopt the ASHRAE 188/CDC Toolkit practices now….we shall see. Thanks, Patsy
Yes, a positive aspect of the shutdowns has been the re-emphasis for water management plans in all types of buildings, not just healthcare. Thanks Patsy!
I feel that points 2, 3 and 4 are essential in the prevention of Legionnaires’ disease going forward. In the UK we have statutory (legally enforceable) documents in place. The main statutes relating to the control of Legionella are as follows:
• The Health and Safety at Work etc Act 1974 (HSWA)
• The Control of Substances Hazardous to Health Regulations 2002 (COSHH)
• The Management of Health and Safety at Work Regulations 1992 (MHSWR)
• The Notification of Cooling Towers and Evaporative Condensers Regulations 1992
To interpret these laws (statutes) we have three main approved codes of practice and guidance documents:
a) Legionnaires’ disease The control of legionella bacteria in water systems Approved Code
of Practice and guidance on regulations ACOP 2013. – ASHRAE Standard 188-2018
b) Legionnaires’ disease Technical guidance HSG274 2014. – ASHRAE Guideline 12-20
c) Health Technical Memorandum 04-01: Safe water in healthcare premises (Parts A, B and
In the UK if a building duty holder fails to apply the measures set out in the above ACOP and guidance documents (or equivalent), they will/can be prosecuted. This promotes the compliance of many organisations. We also have regulators to assure compliance (Health and Safety Executive and the Care Quality Commission). As I understand the situation in America, many organisations do not apply provisions of your standards, which is of concern.
Recommissioning of buildings temporarily taken out of use is included in our guidance document (b) and further guidance has been produced by the European Society of Clinical Microbiology and Infectious Diseases (SEGLI) for managing Legionella in building water systems during the COVID-19 pandemic:
Thanks for taking the time to list the documents, Steve. Yes it’s true that only a small percentage of buildings in the US are implementing a comprehensive water management program per ASHRAE Standard 188. Most do only what is required by law.
Another great article. I think the dry trap issue has been missed along with waste water sources. I cant wait to share this with our customers. Thank you.
Thanks George! And thanks for the good work you all do at estechlab.com!
Matt: Great summary crystallizing the information developed by so many agencies. Another study (early release) pointed to an air conditioning system in a restaurant in Guangzhou, China, which affected 10 persons sitting near an intake/output of an AC unit. It was not clear in the article (https://wwwnc.cdc.gov/eid/article/26/7/20-0764_article) whether the AC was recently put in to use, but certainly points to the importance of maintenance and better filtration. As we approach summer and the beginning of “Air Conditioning Season” we need to be diligent in our care of both AC’s and cooling towers which are all now in the process of starting up.
I believe that environmental sampling for COVID 19 will become as commonplace as environmental sampling for legionella and other pathogens. There are a number of resources for environmental testing available for COVID 19.
Thanks for sharing that, Tom. I’m aware that some hospitals are now testing swabs of surfaces for the COVID-19 virus. There’s still so much to study and learn about it.
A more detailed analysis of the Guangzhou restaurant case by Yuguo Li, et al. can be found. The restaurant has no ventilation (outside air) and the air change rate was very low.
Thanks Traci!
Nicely said. In theory, Legionella prevention could become second nature for all buildings with the standards provided. In reality, my concern is the education and support portion to all of this. Those responsible for maintaining facilities (building owners, maintenance teams, etc.) may still not recognize the importance that these standards and prevention efforts have on health and safety. With many of us here being immersed in the subject of Legionella prevention, it is obvious to us the risk associated with the lack of attention to these details. To others, it may not be as obvious. Education about these topics and making the content relatable to our audience (those actually implementing the standards in their buildings) while also making the implementation of the tasks less of a mountain will hopefully help to see more compliance with the standards. We need to be help building owners, maintenance teams, etc. become educated in this subject and how they can implement it for their buildings specifically.
Totally agree, Erica. We at HC Info are trying to do our part by making water management plans easier to implement via LAMPS tools and training. And your services are a huge help to facilities in setting up and keeping up their WMPs.
I have not had the opportunity to review all documents that have been produced regarding flushing stagnated building water systems. However, the majority of the ones that I have, have all been guidances directing as to “WHAT” you need to accomplish the only one to date that I have found that tells you “HOW-TO-DO” this can be found by accessing The link that I’ve attached from a posting on LinkedIn by Tim Keane referring to chapter 3
Thanks for sharing the link, Michael
Great article especially having all the pertinent information in one handy place as it relates to keeping building water systems and/or features safe for all. The USA citizen going back to work in buildings that have been shut-down really need the facility managers to act per your article. This horrible Covid-19 pandemic is the wake-up call for all public buildings to implement and regularly act upon a comprehensive WMP.
Thanks for commenting, Nina!