Remember: Tap Water Is Not Sterile

Pouring Some Tap Water Into Her Glass

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Key Takeaways

  • Tap water is unsafe for use in medical devices that use water that is inhaled or comes into contact with eye or nasal membranes because they can cause harmful infections. 
  • Common devices that require sterile water include: CPAP machines, neti-pots, humidifiers, and contact lenses.
  • Always follow the medical device manufacturer instructions. 

In a recent survey, the Centers for Disease Control and Prevention (CDC) found that many people have the misconception that using tap water with certain medical devices is safe. The survey results led the CDC to reiterate that tap water is not sterile, and it can lead to infection from waterborne pathogens.

While most of the 1,004 survey respondents agreed that tap water is safe for drinking, cooking, bathing, and hand washing, almost a quarter assumed that it's safe to use tap water to operate medical devices such as continuous positive airway pressure (CPAP), neti pots, and humidifiers.

”Any home device that provides a way for the water to be inhaled or come into contact with mucous membranes of the eyes or nose should use sterile water,“ Kelly A. Reynolds, PhD, a professor and chair of the department of community, environment, and policy at the University of Arizona, told Verywell via email. “When waterborne organisms come into contact with these membranes, or if they are inhaled in the lungs, they can cause serious infections and sometimes death.”

Which Medical Devices Need Sterile Water?

At-home medical devices that treat sensitive areas such as the respiratory tract need to be used with sterile or distilled water that does not contain harmful microorganisms.

Sterile water does not contain microbes, but may contain inorganic materials such as minerals, while distilled water does not contain organic or inorganic materials. 

Devices that need to use sterile or distilled water include:

  • CPAP machines
  • Neti pots
  • Humidifiers 
  • Contact lens cleaning
  • Vaporizers

Common waterborne pathogens, including Pseudomonas aeruginosa and Legionella, can multiply and form biofilms in stagnant water, which create a protective barrier that makes them resistant to disinfectant chemicals and allows the germs to multiply.

The California Department of Public Health told Verywell that following medical device manufacturing instructions is critical to the prevention of waterborne infections. Sterile water is also used for cleaning wounds and for disinfecting many home medical devices. 

Who Is at High Risk of Acquiring Waterborne Infections?

According to the CDC, over 7 million people become ill and 6,000 people die from waterborne infections each year.

While most people will not be affected by germs in tap water, some people are more prone to a serious infection. These include people over 50, infants under six months, current or former smokers, and people who are immunocompromised.

Frequently cleaning, disinfecting, and maintaining medical devices and household items that use water is key to preventing illness, especially among high-risk groups.

“In most parts of a first world country, tap water is likely safe for drinking and cooking,” Michelle Thi Cao, MD, a clinical professor in pulmonary, allergy, and critical care medicine at Stanford Health Care, told Verywell via email. "Boiling water is recommended when using tap water to fill a humidifier system in which an individual directly breathes in the humidified air.”

How and When to Sterilize Tap Water 

Intense weather events can also compromise drinking water. Areas of drought have depleted water sources, leading to an increase in contaminants. Flooding has also caused animal feces, pesticides, and fertilizer to be swept up in water run off.

State and local municipalities are required to inform communities if tap water is unsafe to drink, bathe, and cook with.

Reynolds says that boiling water for three to five minutes is the most common way to sterilize tap water to remove harmful germs, but longer times are required in high altitudes. It is important to store boiled water in clean, sterilized, tightly sealed containers. 

“My best recommendation is to purchase already sterile or distilled water for your home devices,” Reynolds said.

What This Means For You

If you use a home medical device that takes water, it is important to use sterile water to prevent waterborne infections. Always follow the manufacturer instructions for cleaning, disinfecting, and maintained your home medical device equipment.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  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. Emerging Infectious Diseases. 2023;29(2):397-401. doi:10.3201/eid2902.221205

  2. Centers for Disease Control and Prevention. Germs that can contaminate tap water

  3. Centers for Disease Control and Prevention. Preventing waterborne germs at home.

  4. Collier SA, Deng L, Adam EA, et al. Estimate of burden and direct healthcare cost of infectious waterborne disease in the United States. Emerging Infectious Diseases. 2021;27(1):140-149. doi:10.3201/eid2701.190676

  5. Physicians for Social Responsibility. Climate change contaminates your water

By Amy Isler, RN, MSN, CSN
Amy Isler, RN, MSN, CSN, is a registered nurse with over six years of patient experience. She is a credentialed school nurse in California.