Empty Buildings During the Pandemic Mean Stagnant Water and the Risk of Different Diseases

With many non-residential buildings shut down, as the COVID-19 pandemic keeps people home, the water left in the pipes of these unoccupied or low-occupancy spaces stagnates. This may lead to a host of new problems, including an increase in waterborne diseases.

Water stagnation in buildings happens during times of normal occupancy, but for obvious reasons, it is at a much higher rate now. This has two Purdue University researchers concerned – and asking new questions.

Andrew Whelton, an associate professor of civil engineering and environmental and ecological engineering, and Caitlin Proctor, a postdoctoral fellow, are looking at how the COVID-19 pandemic and water stagnation are affecting building water quality. They hope to better understand the consequences of shutting down to ensure safe water when buildings do reopen.

In this Q&A, we asked Whelton and Proctor to explain this problem and what can be done about it. It is part of our blog series to better understand how the COVID-19 pandemic is affecting water resources in unexpected ways.

How did you know your questions about building water quality would be important during these times?

Proctor: A lot of good practice and research out there says don’t let the water sit still. Because we knew that, we said ‘oh wow, the water is going to sit so still in so many buildings.’ So it just triggered in our brains that this could be a big problem.

Whelton: There’s not really much known about building water quality changes for commercial or residential buildings – whether it be a weekend away from your office, a weekend away from your gym, or overnight stagnation. We have been working in buildings where they have had drinking water safety problems after just two days. With the COVID pandemic requiring low occupancy, buildings that didn’t shut down have 80-90 percent less occupancy, and they’re only using 30 percent of the water they typically use. If we had problems before, it’s logical that we’re definitely are going to find more problems nowadays.

Before COVID-19, what was the research saying already about the risks of stagnant water in buildings?

Proctor: Literature would say that if you let the water sit in a copper pipe, there is going to be copper in the water, especially if there is a certain water chemistry that allows a leaching reaction to happen. If your service line is lead and you let water sit, there is going to be lead in the water.

Some of the harmful organisms that grow [in stagnant water] that we’re worried about are Legionella pneumophila, Mycobacterium avium, Pseudomonas aeruginosa, and some amoeba. These can cause disease, and the ways we’re exposed to them are through inhalation or dermal exposures, primarily. Therefore, showering can be more problematic than drinking.

How do we move forward to ensure water quality and safety as we start to reopen buildings? 

Proctor: There is guidance being released, and a lot of it says flush your building before people are allowed back in, and you might have to do that over and over again. The more fresh water you get in, the less likely you are to have problems. One of the challenges with COVID is that it’s not just in your building where the water is sitting still. The pipes outside of your building – those under the street, delivering water to your neighbors – are also sitting still. We know some utilities in Europe are adding extra chlorine to their water to try to combat this, to hopefully allow for some chlorine to be in the water by the time it gets to the building. There are some other actions, such as shock disinfection, that might be considered, but those might be a little more extreme.

Whelton: Some people are talking about draining their plumbing, especially on University campuses, where they don’t expect dorms to be inhabited for a long time. If you drain plumbing, generally it leaves a little moisture in the pipes, and that can breed harmful organisms. This can cause corrosion damage, and it can result in depressurizing the system, which could lead to joints cracking. Draining plumbing is a pretty extreme way to go for large buildings. I know people do it in summer homes, but I would agree like Caitlin said, flush, flush, flush. If you can try to mimic people being in the building to some degree, that’s a good thing.

Regardless of what you decide to do, you’re definitely going to have to change out point-of-use filters and clean devices. You’ll need to clean the aerators; unscrew the aerators and clean off the gunk that’s in there. This should happen before people go back. You really shouldn’t reenter a building that has sat stagnant for months without someone going in first and doing some work to make sure the water system doesn’t harm people.

Are there any other concerns or precautions you’d like to share?

Proctor: One thing that is important is the responsibility for this is shared. The utilities can do some actions to make sure the water in their distribution systems is safe. They can also communicate with building occupants. Facilities or building owners have some responsibility to move the water before occupants are allowed to be exposed to it. The workers who are doing the flushing might need to be protected; they might need masks. I think the Occupational Health and Safety Administration recommends masks if legionella is suspected, for example. There are a lot of different stakeholders who can be involved in preventing waterborne disease. Public health departments might also put out guidance for building owners, so they know what to do. Another point to emphasize is, if there is a slow ramp-up of building occupancy because we’re still trying to distance ourselves, then you’re still going to have low water use and you’re going to need to do something about it. It’s not just the complete shutdown that we’re worried about, but also the slow ramp-up period.

Whelton: The concern is that, under normal conditions, your building may have a problem and you don’t know about it because you didn’t test for it; perhaps you didn’t have to or you assumed everything was okay. Under now prolonged stagnation conditions, those problems may become significant. So that’s why it’s good to flush, get all that old water out. Returning the building to normal water use is going to take some time. It’s not going to be like a light switch and everything’s going to be okay. If you can reduce the problems that may have developed, over time you can get your system back to safe use.

For more details on the study itself take a few moments to view this video.

These answers have been edited for clarity and brevity.