How winter weather can affect your drinking water

Correction: A previous version of this story stated that Legionnaires’ disease is caused by ingestion of contaminated water. It is in fact caused by inhalation. We regret the error.
Washington, D.C. Memphis, Tennessee. Vandalia, Ohio. Breaux Bridge, Louisiana. Kalamazoo, Michigan. In the last month, residents in all of these cities were instructed to boil their drinking water due to safety concerns.
Boil water advisories are common in the U.S., and rarely a cause for concern. These advisories aren’t necessarily straightforward, however, said Jasen Kunz, the lead expert on drinking water at the Waterborne Disease Prevention Branch of the Centers for Disease Control and Prevention. Drinking water regulations are set by the Environmental Protection Agency, but each state has agencies that maintain their own standards within those bounds, Kunz said.
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In addition, factors like climate change and the age of infrastructure can impact how often boil water advisories are (and will be) implemented, said Steve Via, director of federal relations for the American Water Works Association. That’s why you might see a cluster of boil water advisories at once, such as when parts of the South are under stress from winter storms.
PBS NewsHour asked infrastructure and drinking water experts to explain the science behind boil water advisories, how to keep your drinking water safe, and why climate change might make this problem more common.
Utilities must comply with a laundry list of state and federal regulations to provide safe water to customers. When any of those things goes south – a water main breaks, pipes burst or certain contaminants enter the water supply – municipalities might issue boil water advisories. Boiling the water can kill possible pathogens, making the water safe for consumption.
Your household can get prepared now before a water emergency happens. Steve Via of the American Water Works Association suggests these steps:
Often, they’re precautionary notices, as in the case of Memphis’ boil water advisory this winter, said Doug McGowen, President and CEO of Memphis Light, Gas and Water. That advisory was the city’s third in four years, all of which were triggered by uncharacteristically intense winter storms in the area.
Each time they issued an advisory, there was no evidence that the water wasn’t safe. But because the water pressure had dropped below the regulatory standard, MLGW couldn’t say with 100 percent certainty that microbes hadn’t gotten in the supply.
There can be many reasons for a boil water advisory, but often they’re caused by low water pressure. Functional water systems maintain high levels of pressure within the pipes. If too many pipes break, the water leaves the system too fast, and the pressure levels drop, McGowen said.
When the systems work properly, the high pressure keeps groundwater from seeping into the pipes. But when the water pressure drops, groundwater can leak back into the pipes, potentially making the water unsafe for human consumption. For the most part, boil water advisories are issued because of concerns about possible microbial contamination, Kunz said.
A boil water advisory is taped to a water fountain in a classroom building at Albright College due to a water main break in Muhlenberg Township. Photo by: MediaNews Group/Reading Eagle via Getty Images
When other contaminants threaten drinking water, such as lead, petroleum, diesel fuel or harmful chemicals, officials may issue different warnings, even up to “do not drink” water advisories.
Outbreaks caused by microbes in drinking water are rare, Kunz said. Such illnesses caused by water primarily are due to a layer of film on the inside of pipes. Under certain conditions, pathogens in that film can enter the water supply, causing sickness such as Legionnaires’ disease when droplets are inhaled.
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Other potential pathogens that can be ingested from contaminated drinking water include bacteria such as shigella and viruses such as norovirus, according to the CDC. Officials also may be worried about fecal contamination, as well as parasites such as Cryptosporidium, Kunz said. Many of these illnesses can cause intense gastrointestinal distress.
The best way to avoid illness is by following the advice of local health officials and by maintaining your personal water system, he said. Flush unused pipes and your water heater, clean your sink’s aerators and faucets, and follow CDC precautions when using neti pots and humidifiers.
“All of those steps are what people can take within their homes, their apartments, et cetera, to reduce their risk on a day-to-day occurrence,” Kunz said.
Resident Seana Padberg walks by empty shelves where water has sold out at a grocery store in Portland, Oregon May 23, 2014. Some 670,000 residents in Portland, Oregon, and nearby suburbs were instructed to boil their water before drinking it because of possible fecal contamination, the city’s Water Bureau said. Photo by Steve Dipaola/Reuters
If the water is going in your mouth either directly or by surface contact, use boiled or bottled water, the CDC advises. That includes all water for cooking, washing dishes by hand, drinking and brushing your teeth. Unboiled tap water is fine to use for laundry and in dishwashers that have a “sanitize” setting, the CDC says. You also can shower with regular water, but make every effort to not swallow any.
If you have more specific questions, consult the CDC’s fact sheet on boil water advisories.
Winter storms with freezing temperatures can disrupt water infrastructure in many ways. Take Memphis as an example.
Before the city was struck with three unusually intense storms in the last few years, Memphis had never issued boil water advisories, McGowen said. But each storm caused a different problem with its water infrastructure. In early 2021, an arctic blast froze local wells that draw groundwater. At the end of 2022 – on McGowen’s ninth day on the job, he noted – the city briefly imposed rolling blackouts to conserve electricity, but even with backup generators, there wasn’t enough power to keep the pumping stations and wells running. They also faced a water main break.
This January, several inches of snow prompted a state of emergency, and frozen pipes burst, causing water pressure to drop and blocking distribution.
“If there was a pipe in between the MLGW production site and a customer that was broken, you can’t reroute water past that break to get it to someone’s house, so they did not have water,” McGowen said.
Volunteer Elizabeth Murray helps hand water to local residents at Butler Stadium after the city of Houston implemented a boil water advisory following an unprecedented winter storm in Houston, Feb. 21, 2021. Photo by Adrees Latif/Reuters
It’s possible, Via says. Rising sea levels can affect the water table and increase pressure on pipes.
Plus, climate change can affect the frequency and intensity of winter storms. Prolonged cold temperatures, or unusually cold temperatures in areas that aren’t accustomed to that weather, can rapidly freeze and thaw pipes, leading to cracks and bursts.
That’s why cities like Memphis are working on winterizing their water infrastructure, McGowen said.
Age can contribute to structural deterioration, and consequently higher rates of bursting pipes, Via said, but “infrastructure is continually being replaced.”
Each community needs to evaluate when the pipe was installed, what the pipes are made of, what soil they’re in, what pressures they’re under and other factors, he said.
“Particular vintages of pipe have different flaws and strengths. So there’s some World War II-era materials that were makeshift materials and so they have a higher break rate.”
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Some community systems are still on the upward swing of replacing installations from the mid-1900s, he said, while others have been replaced and still others will need replacing.
Making those changes can be costly, and can involve lowering the depth at which pipes are buried to provide natural insulation, adding materials to insulate pipes and wells, and replacing or installing more water pumps and wells. After the 2021 storm, MLGW substantially increased water production, but the 2024 storm taught them they may need to increase it even further, McGowen said.
It’s also not always easy to know when to replace pipes, McGowen said. Utilities try to straddle the line of preventing failure while still getting a good return on investment for their infrastructure.
“At what point do you determine the number of leaks in a line necessitates this replacement? You don’t want to shorten the lifespan of your investment, but you also don’t want to suffer a break,” he said. “What they’re working on in the industry is trying to determine what’s our best mode of pre-failure detection.”