Preventing Waterborne Germs at Home

Plumbing under a sink

The United States has one of the safest tap water supplies in the world. However, waterborne germs can live and grow in our pipes and in devices we use that require water, like humidifiers. Some of these germs can be harmful and cause people to become ill.

Germs especially like to live and grow in water when it is stagnant (not flowing) or when it is not treated with enough disinfectant, like chlorine. It is important to know where your tap water comes from and how to safely use it for purposes other than drinking.

How do germs live in pipes?

Sometimes waterborne germs live together in a group, known as a biofilm. A biofilm is a group of microorganisms—often a mix of bacteria, fungi, and amebas—that live together and release a slimy, glue-like substance, which allows them to stick to surfaces. This slimy “home” acts as a barrier to water treatment chemicals, like chlorine, helping the germs survive and multiply.

A biofilm is more likely to grow abundantly in places where water does not move, such as the inner surfaces of water pipes, water storage tanks, or water heaters.

Some potentially harmful germs that can grow and multiply in your home’s water system (and the types of illnesses they cause) include:

Waterborne germs can grow in pipes

According to federal and state laws, public water utilities must provide water that meets certain quality and safety standards for drinking purposes. However, tap water is not sterile, meaning it might have germs in it. Even when the public water system is working correctly, a small number of germs that naturally occur in the environment can still be present.

When these germs get into the pipes inside a home or building, they could grow and multiply if the conditions are right. For example, this can happen when the taps are not turned on for long periods of time and the water sits still within the pipes.

Some waterborne germs can make you sick

Most people may know that harmful waterborne germs can cause stomach illnesses, like vomiting or diarrhea, if they are swallowed. But these germs can also cause illnesses of the lungs, brain, eyes, or skin. When you turn on the water, particularly if water has remained stagnant in your home’s pipes for longer than normal (for example, a week or more), germs from biofilm (see green box titled “How do germs live in pipes?”) can come out of the faucet, showerhead, or other water devices. Some of these germs can make people sick when the water:

  • Is inhaled as a mist
  • Comes in contact with an open wound
  • Goes up the nose (for example, when using a neti pot)
  • Is used to rinse or store contact lenses, or is splashed in your eyes while you are wearing contacts

People at risk for getting waterborne illnesses

Most healthy people exposed to the germs that live in pipes do not get sick. However, certain groups of people may be at increased risk for infection. These groups include:

  • People 50 years or older
  • Current or former smokers
  • People with a chronic lung disease (like chronic obstructive pulmonary disease [COPD] or emphysema)
  • People who have health problems or take medicines that lower their body’s ability to fight germs and sickness—such as people whose immune systems are weakened because of cancer, an organ transplant, or HIV
  • People with underlying illnesses such as diabetes, kidney failure, or liver failure
  • Infants under 6 months old
  • Contact lens wearers

Steps to protect yourself and others from waterborne germs at home

You can take steps to protect yourself from waterborne germs in your home, including:

Flush your faucets and showerheads if they have not been used recently

If a faucet or showerhead in your home has not been used for longer than normal (for example, a week or more), flush the faucet or showerhead before using it for the first time. Open the cold water tap fully and adjust as necessary to avoid water overflowing or splashing. The cold water should run for two minutes. Turn off the cold water and open the hot water tap fully, adjusting as necessary to avoid water overflowing or splashing. Run the water until it starts to feel hot and then turn it off.[1] If your faucet or showerhead has one handle that controls both hot and cold water, follow the same steps. Put the handle all the way to the “cold” setting and run the water for two minutes; then move the handle all the way to the “hot” setting and run the water until it starts to feel hot.

Clean, disinfect, and maintain all devices that use water

You can help prevent exposure to waterborne germs in your home by:

  • regularly cleaning all devices that use water to remove dirt, debris, germs, and other impurities
  • disinfecting the devices by killing germs, and
  • storing and using the devices as recommended by the manufacturer

Always follow the manufacturer’s recommendations regarding the proper use, cleaning, and maintenance of your water-related devices, such as:

  • Portable humidifiers
  • Neti pots/nasal rinses
  • Showerheads and faucet aerators
  • Water heaters

[1] This flushing estimate was adapted from work previously conducted by the Water Research Foundation (Project 4572). Flushing Guidance for Premise Plumbing and Service Lines to Avoid or Address a Drinking Water Advisory pdf icon[PDF – 93 pages]external icon. 2018

What about water filters?

Most home water filters are not designed to remove germs from your water. They typically use a carbon filter to remove impurities like lead or to improve the taste of your water. Germs that live in biofilms can grow and multiply in these devices when they are not properly maintained and replaced according to the manufacturer’s instructions.

Common types of water filters include:

  • Pitcher and countertop filters
  • Refrigerator and icemaker filters
  • Under sink filters
  • Showerhead and faucet filters

There are also whole-home water filters, which are installed at the point where water enters your home so that all the water coming out of every tap and showerhead is filtered. Some whole-home water filtration systems remove water treatment chemicals, such as chlorine. If you decide you want a water filter, knowing what you need or want from your water filter is an important first step to choosing the right one.

People with weakened immune systems should consult with their healthcare providers as well as a water disinfection specialist to determine whether they should consider installing a specialized whole-home water filtration system.

More information about home water filters is available on CDC’s Guide to Water Treatment Technologies for Household Use and Choosing Home Water Filters and Other Water Treatment Systems pages.

Portable Humidifiers

Germs can live in humidifiers unless you empty them of all water daily, clean them properly on a regular basis, and allow them to air dry after cleaning. These germs can spread through the mist created by the humidifier when you turn it on.

Follow the manufacturer’s instructions for cleaning, disinfecting, and drying your humidifier to prevent germs from growing and spreading. Consider using distilled or previously boiled (and cooled) water or water disinfected with chlorine bleach in portable humidifiers.

Neti Pots/Nasal Rinses

Always follow the manufacturer’s instructions when using and cleaning neti pots or nasal rinses. Only use distilled, previously boiled, or filtered water (using a filter that is meant to remove common germs) to rinse sinuses.

Showerheads and Faucet Aerators

Clean showerheads and faucet aerators (the mesh screen screwed into your faucet that helps with water flow) whenever buildup is visible to help prevent germs from growing within the faucet. This might require you to remove the showerhead and hose and soak in a solution (such as white vinegar) to remove buildup. Follow the manufacturer’s instructions for cleaning.

Water Heaters

Set the Water Heater Temperature

Keeping your home’s water heater temperature set at an appropriate level can help reduce the growth of some germs (such as Legionella). A hotter water temperature of 130–140°F can kill many harmful germs, but also increases the risk of scalding. If you set the water heater above 120°F, make sure you take extra precautions to mix cold and hot water (using thermostatic valves) at the faucet or shower to avoid scalding. This is especially important if young children, older adults, or other people at increased risk of scalding live in your home. Ask your healthcare professional about your risk of Legionella infection to determine the best course of action.

Flush the Water Heater

Regularly flushing your water heater can extend its life and is recommended by most manufacturers. If you decide to flush your water heater, make sure to follow the manufacturer’s instructions or have a professional do the work. Many manufacturers recommend flushing your water heater:

  • Annually
  • Before you move into a home
  • After plumbing work
  • If the water is discolored

Communicate with your water utility

Sometimes there are disruptions to the flow of water into your home. These can be planned (for example, your water utility makes repairs to the water system) or unplanned (for example, a water main breaks). Germs may be able to enter the pipes in your home during these disruptions. You can take steps to stay informed about what is happening with your pipes and ensure the water in your home is safe to use:

  • Sign up to receive messages and advisories (e.g., boil water advisories) about your water. This may require opting-in with your utility or local government alert system.
    • Follow all recommendations related to water use during the advisory.
  • Contact your water utility if you notice a decrease in water pressure throughout your home or you see brown or discolored water.
    • After a loss in water pressure, flush water through each faucet and shower in your home until it starts to get hot and runs clear (there is no discoloration). Contact your water utility for additional recommendations.

Keep private water sources safe

Homes that use private wells or other private sources of water have different considerations than those served by public utilities. The safety of water in these private sources is the responsibility of the homeowner. Guidance and recommendations to keep well water safe are available from CDC.