As Buildings Reopen, Stagnant Water May Harbor Unseen Risks
After sitting empty for months, offices and commercial buildings in St. Louis are beginning to reopen — many with freshly installed Plexiglas barriers to protect workers from passing the coronavirus.
But researchers warn of other health risks that may be lurking in the plumbing systems of these once-shuttered buildings.
With fewer users, pipes have held stagnant water for weeks or months at a time. Some waterborne pathogens thrive in this environment, while heavy metals can slowly leach out of aging pipes. The sheer number of unoccupied buildings during the pandemic has some researchers concerned about a potential spike in waterborne illnesses.
Fangqiong Ling, an assistant professor in Washington University’s McKelvey School of Engineering, has spent her career studying bacteria in stagnant water.
It’s still unclear, she said, how these complex communities will change over a period of months.
“Previously, we were thinking more about stagnation for weeks,” Ling said. “Stagnation for months is a new question.”
Some pathogens, such as Legionella pneumophila, which causes the sometimes-deadly Legionnaires’ disease, grow in stagnant lukewarm water inside plumbing systems. People become ill when they inhale tiny water droplets containing the pathogens, often in steam or mist.
In 2015, dozens of staff and residents contracted Legionnaires’ disease at the Illinois Veterans Home in Quincy — an outbreak that left 12 residents dead.
Despite high-profile cases, the disease remains relatively rare in the U.S., with about 9,933 cases in 2018, according to the most recent data available from the Centers for Disease Control and Prevention.
Legionnaires’ disease often affects people with compromised immune systems more severely, however, which could make COVID-19 patients and survivors more vulnerable to getting sick, said Purdue University postdoctoral researcher Caitlin Proctor.
“This could definitely be a potential issue, especially for asymptomatic people who are returning to work without realizing that they're infected,” said Proctor, who is part of a team studying water quality in unoccupied buildings during the pandemic.
Flushing out water systems
Water treatment plants typically add small amounts of disinfectant to keep bacteria from growing, but these chemicals degrade in stagnant water.
“When you don't have fresh water coming into the system periodically, these measures are less effective,” Proctor said. “We’re definitely concerned about more bacterial growth that would happen during stagnation.”
Some buildings, like schools, close temporarily for a few months every year and may have plans in place to flush water systems.
St. Louis Public Schools, for instance, has a preventative maintenance program that “includes flushing of the drinking water on a routine basis — after summer, breaks, weekends and even daily prior to food preparation,” an SLPS spokesperson said.
The school system has also hired a consultant to test water quality before students and staff return, the spokesperson said.
But many of the buildings that closed during the pandemic — theaters, gyms, offices — rarely have stagnant water sitting in their pipes for more than a few days, Proctor said.
“The problems that we're thinking about tend to be worse in large buildings that have complicated plumbing,” Proctor said, adding that many building managers “would not be used to it and would not have a plan for dealing with it.”
The St. Louis Metropolitan Sewer District does not have specific guidelines for reopening unoccupied buildings, a spokesperson said, but several federal agencies have released recommendations.
Regularly opening the water taps and flushing toilets can help keep water flowing and prevent bacteria and heavy metals from accumulating.
Before reopening, property owners and managers should also conduct a “systematic flush” of all water systems in the building, Proctor said, including appliances that use water, such as dishwashers and ice machines.
“It’s good to pay attention, but it’s not necessary to be super alarmed,” Ling said. “Going into a building that hasn’t been used for two months and immediately filling up a humidifier, though, that’s a bad idea.”
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