Why You Shouldn't Use Tap Water in Humidifiers, Neti Pots, or Other Home Medical Devices

Water from the tap is safe to drink, but it may not be safe for other uses.

  • Many Americans are unaware that tap water is not intended for use in many home medical devices, including nasal rinsing devices, CPAP machines, and humidifiers, new research shows.
  • Though safe for drinking and cooking, tap water in the U.S. may contain pathogens harmful when inhaled, or when used to rinse eyes or nasal passages.
  • To make tap water safe for use in home devices, boil it for at least one to three minutes, depending on your altitude.
woman sleeping with humidifier running

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Too many Americans may be using tap water in their home medical devices—including nasal rinsing devices (neti pots), contact lens cases, and vaporizers or humidifiers—despite it being unsterile and potentially dangerous, new research shows.

The findings come from a new CDC study, published in the journal Emerging Infectious Diseases. Researchers surveyed just over 1,000 people in the U.S. about their perceptions of tap water and its safety or sterility.

One-third of individuals—mainly those who identified as men, were from urban areas, or were African American or Black—incorrectly said they believe tap water does not contain bacteria or other living organisms.

More than half of respondents (62%) said tap water can safely be used to rinse sinuses; 50% said it can be used for rinsing contact lenses, and 42% said it can be used for respiratory devices. Additionally, 24% of respondents said they’ve actually used tap water in their humidifiers or CPAP machines before.

The data suggests the need to further inform people of what tap water should and should not be used for in a home setting.

“This information is not intended to scare anybody or make people feel that their tap water isn’t safe for drinking, cooking or bathing,” study co-author Shanna Miko, DNP, MPH, an epidemic intelligence service officer at the Centers for Disease Control and Prevention, told Health. “We just want people to know there are natural pathogens that exist in the environment and they make their way into our pipes.”

Pathogens in Tap Water

Although tap water in the U.S. is treated to meet safe standards for drinking, cooking, and bathing, low levels of certain microorganisms remain in water systems, wells, and plumbing.

While those microorganisms are mostly safe for drinking and cooking, they may not always be so safe when used in medical devices that aerosolize water, or in eye or nose irrigation.

It’s estimated that these biofilm-associated pathogens are responsible for a large portion of the 120,000 hospitalizations and 7,000 deaths each year in the U.S. due to waterborne diseases.

Biofilm: Clusters of microorganisms that live together under a gluey, slimy layer that acts as a defensive barrier. In a biofilm, pathogens like bacteria can go dormant, increasing their ability for survival. The biofilm is also protected against disinfection or treatments, allowing the microorganisms to survive and live to infect hosts in the future.

According to Anastasia Wasylyshyn, MD, a clinical assistant professor of infectious disease at Michigan Medicine in Ann Arbor, who was not involved in the new study, the types of pathogens present in your tap water depend on local water treatment practices as well as geographic location. 

“Pathogens like Naegleria fowleri—a ‘brain eating amoeba’—can be common in areas with warm water year round, like the Southern U.S.,” Dr. Wasylyshyn told Health

Infections from Naegleria fowleri are rare but deadly—when someone is infected, it’s usually fatal. Though most Naegleria infections are associated with swimming in warm lakes or rivers, they have been linked to nasal rinsing.

Other waterborne pathogens that have caused illness when used in at-home medical devices include the genus Pseudomonas—which includes more than 200 different speciesLegionella pneumophila, the pathogen that causes Legionnaires disease, and a group of pathogens called nontuberculous mycobacteria, which can cause pneumonia.

There is, however, an “active surveillance system for many of these types of pathogens in all parts of the U.S.,” said Dr. Wasylyshyn.

According to Miko, both the CDC and the Environmental Protection Agency (EPA) are also working to understand how aging pipes may become breeding grounds for pathogens—a relatively new problem for the country’s water infrastructure.

“A lot of piping in the U.S. is well over 50 years old. When you constantly run water through those pipes, you will have a natural accumulation of pathogens that naturally live in the environment and unfortunately most pathogens are able to adapt and evolve,” Miko said. “We really need more research to understand what this means for us in the future.”

Climate change is also causing warmer temperatures and making flooding more common, which increases the chances that runoff will wash pathogens into tap water sources.

How to Make Tap Water Safe for Medical Devices

How dangerous the waterborne pathogens found in tap water are to an individual depends on many factors, including that person’s age, health, and the type of device they’re using.

“Any device that is going to blow or direct water directly into your body is of higher concern than a device like a humidifier that is acting in a single room or in a whole house,” said Wasylyshyn.

People who are elderly, babies less than 6 months old, and people who have weakened immune systems are all at a higher risk as well and should take extra precautions to ensure any tap water they use in medical devices is properly treated, said Miko,

“For people that have healthy immune systems, it’s not that big of a risk,” said Miko. “[But] we want to make sure that people who are a little more vulnerable to the pathogens we sometimes find in our pipes understand that there are a few extra steps they can take when using this water for medical devices.”

These steps are relatively easy, and don’t include the need to purchase distilled water or expensive purifiers, said Miko. All safe-to-use water really requires is some heat.

The CDC standard for safe water is to boil it for one minute if you live below 6,500 feet. If you live at higher elevation, boil the water for three minutes. Then, let the water cool before using and store it in sanitized containers.

If you’re curious about the water in your area, public water is routinely tested for bacteria and the results are publicly available. Each year you have access to a Consumer Confidence Report, provided by the EPA, on your local drinking water quality and any contaminants found in the water.

However, if you have well water, the testing may be up to you. “People who have private water are advised to have their water tested regularly,” said Dr. Wasylyshyn. “The local or county health department can organize that for you or provide references.”

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  1. Miko S, Collier SA, Burns-Lynch CE, et al. (Mis)perception and use of unsterile water in home medical devices, PN View 360+ survey, United States, August 2021. Emerg Infect Dis. 2023;29(2). doi:10.3201/eid2902.221205

  2. Polivache H, Van Bambeke F. Dangerous slimes: how bacterial biofilms make you sick and how to combat them. Front Young Minds. 2020;8(62). doi:10.3389/frym.2020.00062

  3. Centers for Disease Control and Prevention. Ritual nasal rinsing & ablution.

  4. Girard L, Lood C, Höfte M, et al. The ever-expanding Pseudomonas genus: description of 43 new species and partition of the Pseudomonas putida group. Microorganisms. 2021;9(8):1766. doi:10.3390/microorganisms9081766

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