COVID19 Key Warnings for Building Water SystemsThe 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

ASHRAE. 2018. Standard 188. Legionellosis: Risk Management for Building Water Systems. Atlanta: American Society of Heating, Refrigerating and Air-Conditioning Engineers.

ASHRAE. 2020. Guideline 12-2020. Managing the Risk of Legionellosis Associated with Building Water Systems. Atlanta: American Society of Heating, Refrigerating and Air-Conditioning Engineers.

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.

DeMarco P. 2020. Understanding Coronavirus Exposure for Plumbing Professionals. PHCP Pros. March 20, 2020.

ESGLI. 2020. ESGLI Guidance for managing Legionella in building water systems during the COVID-19 pandemic. ESCMID Study Group for Legionella Infections.

George R. 2020. Press Release: Flushing Bacteria from Stagnant Building Water Piping. Monroe, MI: Plumb-Tech Design & Consulting Services LLC. April 22, 2020.

Gormley M, Aspray T, Kelly D. 2020. COVID-19: mitigating transmission via wastewater plumbing systems. The Lancet, March 23, 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 4.038 Flushing Domestic Water Systems of Potentially Contaminated Water after Incidents or Shutdowns

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

PHE. 2020. COVID-19 and Food Water and Environmental Microbiology Services. Public Health England. March 30.

Proctor C, Rhoads W, Keane T, et al. 2020. Considerations for Large Building Water Quality after Extended Stagnation.

Purdue University, Center for Plumbing Safety. Flushing Plans.

UA. 2020. Guidelines to Protect Worker Health Related to Coronavirus (COVID-19) and Other Potential Infectious Material (OPIM) in Plumbing and HVAC Systems. Annapolis: United Association.

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.

WHO. 2020. Water, sanitation, hygiene and waste management for the COVID-19 virus. Technical brief. March, 2, 2020.

Yu ITS. 2004. Evidence of Airborne Transmission of the Severe Acute Respiratory Syndrome Virus. New England Journal of Medicine 350:1731-1739.


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