While water from your tap generally is safe to drink, you should not use it for at-home medical purposes like sinus rinsing, washing contact lenses, and filling respiratory devices. But new research suggests that many Americans – wrongly – think tap water is safe for such uses.
In a survey of 1,004 adults in the U.S., about one in three people said that tap water did not contain bacteria or other living organisms, and 26% said water filters removed these microbes and thus sterilized water. Both statements are false: Tap water may contain some microbes, and water filters cannot remove these living organisms from water.
Tap water goes through a multistep treatment process that makes it safe for us to drink, and it must meet strict safety standards before leaving a water treatment plant. But germs that naturally exist in the environment can remain.
As tap water travels through miles of pipes all the way to your faucet, it can pick up waterborne microbes, says Shanna Miko, DNP, of the Waterborne Disease Prevention Branch at the CDC’s National Center for Emerging and Zoonotic Infectious Diseases. Bottled water is held to the same standards and is also not considered sterile, she says.
Our bodies encounter germs every day, and most healthy people exposed to those found in pipes do not get sick. But some groups might be at a higher risk for infection, like people age 50 or older, infants under 6 months old, current and former smokers, people with a weakened immune system, or those with diabetes, liver failure, or kidney failure.
“When we have this combination of vulnerable populations and using [tap water] in different ways, like putting it in our eyes or our nasal cavity or inhaling it into our lungs, that’s where the risk occurs,” Miko says.
The CDC advises that water used for nasal rinsing and the filling of respiratory devices should be sterile, meaning that it does not have any bacteria or other living organisms. Contact lenses should only be washed and stored in fresh contact lens solution, and wearers should avoid any water touching their lenses, which includes swimming and bathing.
Still, there are cases where people have gotten infections due to misusing tap water for medical purposes, Miko says. In one extreme case, a woman died after contracting a brain-eating amoeba while using tap water in a nasal-flushing neti pot.
These types of cases are rare, but it is important that the public understands how to “minimize their exposure to those germs at home,” she says, especially if they are particularly vulnerable to infection.
To capture how the American public understands water sterility and how they use tap water at home, Miko and colleagues designed a survey that they sent to people ages 18 and above from Aug. 16 through Aug. 18, 2021. The nationwide sample was then weighted to represent of the U.S. population in gender, age, region, education, race, and ethnicity.
The results of the survey were presented on May 5, 2022, at the CDC’s annual Epidemic Intelligence Service Conference.
About 63% of people correctly answered that sterile water does not contain any bacteria or other microorganisms, and two-thirds knew that tap water could contain these microbes. But there was a disconnect on what was safe for at-home medical use, Miko says.
“Even though they recognized that tap water isn’t sterile, they still agreed that it was OK to use for nasal rinsing and contact lens rinsing or storage and even in respiratory devices like home humidifiers, like the CPAP machines that some people use at nighttime,” she says.
More than half of people (62.4%) said tap water was safe for nasal rinsing, half (50.1%) said it was safe for rinsing contact lenses, and 41.5% said that it could be safely used for medical respirator devices and humidifiers.
But far fewer people reported actually using tap water for these tasks. About one in four (24%) said they filled medical respirator devices with tap water, 12.7% said they used tap water for nasal rinsing, and about 9% said they used it to rinse contact lenses.
The results show “there is a really dramatic need for education of the public relating to tap water,” says Rachel Noble, PhD, who does research on water quality and public health at the University of North Carolina at Chapel Hill. She was not involved in the study.
“It’s pretty clear that most people know that sterile means that nothing is growing in your water,” she says. The confusion, she says, lies in whether tap water can be safely used for medical purposes.
Safe, Sterile Water
While water straight out of the tap should not be used for these procedures, boiling the water is an easy way to kill any bacteria, viruses, or other microbes and make it safe for nasal rising or filling medical respiratory devices, Miko says. The water should be boiled for 1 minute and then left to cool.
If you don’t want to boil your water, you can also purchase sterile or distilled water, which are both safe for at-home medical use. The CDC’s Healthy Water site also has information on cleaning water at home.
While the survey was meant to show how to handle water that’s for at-home medical use, Miko says that tap water is treated and sanitized and “is meant to be safe for drinking, cooking, and self-care like bathing, tooth brushing, and laundry.”
While most healthy people will not get sick from germs they might find in water, the small steps of boiling it or buying sterilized water for at-home medical use can help prevent infections, especially in people at higher risk.
“We don’t want to scare people,” she says. “We just want people to be as healthy as they can be.”
Shanna Miko, DNP (doctor of nursing practice), Waterborne Disease Prevention Branch, National Center for Emerging and Zoonotic Infectious Diseases, CDC.
CDC Epidemic Intelligence Service conference: “Risky Business: Perceptions and Misuse of Tap Water for Home Medical Purposes – PN View 360+ Survey – United States, August 2021.”
Rachel Noble, PhD, University of North Carolina, Chapel Hill.