Waterborne germs can live and grow in our pipes and in devices that use water, such as humidifiers. Some of these germs can make people sick.

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

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. But 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 in the water.

These germs can grow and multiply in the pipes inside a home or building if the conditions are right. For example, this can happen if you don’t turn on the taps for long periods of time and the water sits still inside the pipes.

Sometimes waterborne germs, like bacteria, fungi, and amebas, live together in a group, called a biofilm. A biofilm releases a slimy, glue-like substance. This slime allows the germs to stick to surfaces. The slime keeps water treatment chemicals, such as chlorine, away from the germs, which helps the germs survive and multiply.

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

• Nontuberculous mycobacteria (cause lung, blood, or skin infection)
• Legionella spp. (cause lung infection)
• Pseudomonas aeruginosa (cause blood, lung, or skin infection)
• Naegleria fowleri (cause brain infection)
• Acanthamoeba spp. (cause brain and eye infection)

Most people may know that some 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, especially if you haven’t used the water in a while (for example, a week or more), germs from biofilm 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 someone’s eyes while they are wearing contacts

Most healthy people exposed to the germs that live in pipes do not get sick. However, certain groups of people may be more likely to get an infection. These groups include:

• People 50 years or older
• Current or former smokers
• People with a chronic lung disease (for example, 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 (for example, 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

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

• Flush your faucets and showerheads if you haven’t used them recently
• Clean and maintain all devices that use water
• Communicating with your water utility
• Keep private water sources safe
• Check with your building manager, owner, or landlord

Flush your faucets and showerheads if you haven’t used them recently

If you have not used a faucet or showerhead in your home recently (for example, a week or more), flush the faucet or showerhead before using it for the first time. Turn on the cold water fully and adjust as needed to avoid water overflowing or splashing. Let the cold water run for 2 minutes. Turn off the cold water and turn on the hot water fully. Run the water until it starts to feel hot and then turn it off. 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 2 minutes; then move the handle all the way to “hot” and run the water until it starts to feel hot.

Clean and maintain all devices that use water

To help prevent exposure to waterborne germs in your home:

• Regularly clean all devices that use water to remove dirt, debris, germs, and other impurities
• Store and use the devices as recommended by the manufacturer

Always follow the manufacturer’s recommendations regarding the using, cleaning, and maintaining your water-related devices, such as:

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

Portable Humidifiers

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

Follow the manufacturer’s instructions for cleaning and drying your humidifier to prevent germs from growing and spreading. Consider using distilled or boiled (and then 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 devices to clear or flush sinuses, like neti pots or nasal rinses. Only use distilled, boiled (and then cooled), or filtered water to rinse sinuses. If using filtered water, it is essential to use a filter with a label that reads “NSF 53” or “NSF 58,” or contains the words “cyst removal” or “cyst reduction.”

Showerheads and Faucet Aerators

Clean showerheads and faucet aerators whenever you can see buildup to help prevent germs from growing within the faucet. The aerator is the mesh screen screwed into your faucet that helps with water flow. You may need to remove the showerhead and hose and soak them 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 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, 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 decide on the best course of action.

Flush the Water Heater

Regularly flushing your water heater can make it last longer and is recommended by most manufacturers. If you decide to flush your water heater, 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

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

You can also get whole-home water filters, which are installed at the point where water enters your home. That way, all the water coming out of every tap and showerhead is filtered. Some whole-home water filters remove water treatment chemicals, such as chlorine. If you decide you want a water filter, knowing what you want your water filter to do is an important first step to choosing the right one.

People with weakened immune systems should talk to their healthcare provider and a water disinfection specialist about whether they should consider installing a specialized whole-home water filter.

Communicate with your water utility

Sometimes events disrupt 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 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 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 (with no discoloration). Contact your water utility for more recommendations.

Keep private water sources safe

In homes that use private wells or other private water sources, the homeowner is responsible for the safety of the water.

Check with your building manager, owner, or landlord

If you live in an apartment building or other building with multiple housing units, you can talk to your building’s owner, manager, or landlord about what steps they are taking to protect residents from waterborne germs.

Much of the water we use comes from the ground. Learn more about the importance of groundwater, the threats to its safety, and how to protect its sources.

Water is one of the world’s most precious resources. People use water every day for many activities, such as drinking, bathing, recreation, agriculture, cooling, manufacturing, and medical uses. Although water plays an essential role in everyday life, many people don’t realize that much of their water comes from the ground.

Groundwater is water found below the earth’s surface in spaces between rock and soil. Surface water is water that collects above the earth’s surface, such as streams, rivers, lakes, or oceans. Thirty percent of all the fresh water on Earth is groundwater, while the other 70% is surface water. Groundwater supplies water to wells and springs and is an important source of water for public water systems and private wells in the United States.

An estimated 145 million Americans get their tap water from a groundwater source.

Groundwater Contamination

All groundwater sources should be protected from contamination (germs and harmful chemicals).

Protecting the safety of groundwater is an important priority for countries throughout the world, including the United States. Most of the time, U.S. groundwater is safe to use. However, groundwater sources can become contaminated with germs, such as bacteria, viruses, and parasites, and chemicals, such as those used in fertilizers and pesticides. Contaminated groundwater can make people sick.

Groundwater sometimes contains naturally present germs and harmful chemicals from the environment, such as arsenic and radon. More often, however, human activities contaminate ground water. These human causes can include incorrect use of fertilizers and pesticides; poorly situated, constructed, or maintained septic systems; improper removal or storage of wastes; mining and construction; and chemical spills at work sites.

Contamination of groundwater systems can lead to outbreaks of disease. Previous outbreaks have occurred either because the groundwater was untreated or because of problems with water treatment. The most common germs identified in groundwater outbreaks include:

• Shigella
• Hepatitis A
• Norovirus
• Giardia
• Campylobacter
• Salmonella

Other germs that cause outbreaks from groundwater include Cryptosporidium (a parasite), E. coli (a bacterium), and assorted viruses. From 2009 to 2017, 143 outbreaks linked to groundwater systems were reported to CDC.

The presence of germs and harmful chemicals in our groundwater can lead to health problems, including diarrhea, reproductive problems, and nervous system disorders. Infants, young children, pregnant women, the elderly, and people whose immune systems are weakened because of HIV/AIDS, chemotherapy, or transplant medicines may be more likely to get sick from certain germs and chemicals.

Is Your Water From a Groundwater Source?

Public Water Systems

One-third of Americans — more than 102 million people — get their drinking water from public water systems that use groundwater. The EPA regulates drinking water quality in public water systems. You can find out more about your local drinking water quality and possible contaminants by viewing your Consumer Confidence Report (CCR), which most utility companies are required to provide to customers.

Private Wells

An estimated 43 million Americans get their water from private groundwater wells, which are not subject to EPA regulations. Private groundwater wells can provide safe, clean water. However, contamination that can cause sickness also can occur in well water. If you have a well, you should take steps to protect it and have the water tested annually to make sure your water is safe from harmful germs and chemicals. State and local health departments provide information to help well users protect their drinking water.

Climate change is expected to increase the incidence of water-related illnesses by disrupting marine and freshwater resources. Rising sea surface temperature, changes in frequency and intensity of precipitation, as well as agricultural and industrial runoff from more frequent storms, can create conditions for pathogens to thrive and contaminate bodies of water. These contaminants include bacteria, viruses, protozoa, and toxins, and exposure to them through ingestion, inhalation, or direct contact can cause water-related illness such as vibriosis.

Water Quality Impacts on Human Health

The effects of climate change can impact natural marine, coastal, and freshwater systems as well as manmade water infrastructure designed for treating drinking water, wastewater, and stormwater .

Eutrophication, an overabundance of nutrients, can result from runoff contaminated with fertilizers and pesticides and disrupt natural ecosystems. Excess nutrients can also cause algal blooms that produce toxins and directly contaminate fish and shellfish that humans consume. Ocean acidification, the excess absorption of carbon dioxide, affects marine ecosystems and can also influence the growth of harmful algal species.

Extreme weather events and increased sea surface temperatures affect the growth and spread of pathogens and toxins. In most cases, water contamination and subsequent outbreaks of waterborne illnesses are caused by an extreme rainfall or weather event that produces flooding and releases industrial and agricultural runoff into a body of water. Flooding can overwhelm sewage treatment facilities causing bacteria like Legionella and Escherichia coli (E. coli) to grow and develop in stagnant water, such as in unused pipes.

Exposure to contaminated water can lead to adverse health effects from waterborne illnesses. Swimming or fishing in polluted water sources and consumption of affected seafood are the most common pathways of exposure. Some common water-related illnesses are diarrhea, giardiasis, dysentery, typhoid fever, E. Coli infection, and salmonellosis. Adverse health effects can include pain in the gastrointestinal, reproductive, neurological systems, and other symptoms. Continuous exposure can have long-lasting health impacts.

Opportunities for Public Health Improvement

Public health safeguards can reduce the risk of exposure to waterborne pathogens and toxins and limit outbreaks of water-related illnesses. These efforts can include monitoring and testing water quality following extreme weather events, setting water quality standards for drinking water, issuing advisories for consuming fish and shellfish, as well as enacting guidelines for recreation in a body of water.

Fortifying marine, coastal, and freshwater ecosystems by restoring and protecting wetlands can help reduce greenhouse gases through carbon sequestration. Promoting safe water quality can be accomplished by capturing and treating contaminated runoff, buffering bodies of water from storm surges, and natural filtration of contaminants.

Global Environmental Health

Research, education, training, and research translation directed at health problems that are related to environmental exposures and transcend national boundaries, with a goal of improving health for all people by reducing the environmental exposures that lead to avoidable disease, disabilities, and deaths.

Research Needs

More research is needed to better understand how toxins, pathogens, and chemicals affect marine species, especially those consumed by humans. For example, improved knowledge of the initiation, development, and termination of harmful algal blooms, as well as the exact nature of the toxins associated with them, can shed light on the extent to which people’s health can be affected.

Climate change, sea level rise, and coastal and watershed development are increasing the prevalence of waterborne pathogens. It will be important to evaluate and monitor exposures, especially complex mixtures of contaminants, and associated health risks.

Water-Borne Disease

Water can spread illness when it is contaminated by disease-causing organisms. Water-borne diseases can infect humans and animals that drink or recreate in contaminated water.

General Water-Borne Disease Information

Geographic Distribution

Water-borne diseases are found worldwide.

Hosts and Transmission

Water-borne disease is found in lakes or streams that have been infected by animal or human feces or urine. Many water-borne diseases are also found in contaminated soil, food, and surfaces, or can be passed from person to person.

Drinking untreated water from springs, streams, or lakes while hiking or camping in the parks could put you at risk for infection.

Signs and Symptoms

Water-borne diseases can cause symptoms in humans and animals. Symptoms in humans typically occur within 10 days of infection and can include:

• Diarrhea
• Stomach aches or pain
• Dehydration
• Nausea and vomiting
• Gas
• Weight loss

Prevention and Control

You can lower your risk of getting water-borne illness while visiting the parks by:

• Filtering and disinfecting or boiling fresh water before drinking. Water should be boiled longer at higher elevations.
• Washing your hands before handling or eating food and after using the toilet. Alcohol-based hand sanitizers can be used when soap and water isn't available but are not a substitute for hand washing.
• Cleaning up after pets and keeping them on a leash.
• Viewing animals in the wild from a safe distance and not handling wild animal feces.

Testing and Treatment

Some animals and humans with water-borne illness can get better on their own without treatment. Drinking lots of fluids can help prevent dehydration from diarrhea.

If you think you have the symptoms of water-borne disease and have been exposed to potentially contaminated soil, food, or water, consult your healthcare provider.

One Health and Water-Borne Disease

Human impacts on the environment, including land development and climate change, can contaminate water and decrease the ability of ecosystems and wetlands to naturally filter water. Some of these changes to the land, air, and water promote the transmission and spread of water-borne diseases. By protecting natural environments and their ecological properties and processes, we can help protect ourselves from disease – this is One Health in action.

Water-Borne Diseases

Cryptosporidium

Cryptosporidium, which causes the diarrheal disease cryptosporidiosis or “Crypto”, is a tiny parasite that infects humans and animals worldwide.

Cryptosporidium is found in water, soil, and food, as well as on surfaces that have been contaminated by feces of an infected person or animal.

The major reservoirs for Cryptosporidium in humans are humans, cattle, and sheep. It is also found in lakes or streams that have been infected by human or animal feces. Animals and humans with cryptosporidiosis often get better on their own without treatment in a few days.

Giardiasis

Giardia is a tiny parasite that is found worldwide in water, soil, and food as well as on surfaces that have been contaminated by feces of an infected person or animal. Giardiasis is the most common water-borne disease in the United States.

Humans are the major reservoir for human infections, although other strains from animals may infect humans occasionally. It is spread from person-to-person by hand-to-mouth transfer of cysts from the feces of an infected individual.

Giardia is also found in lakes or streams that have been infected by human or animal feces. Humans with Giardia often get better on their own within a few weeks.

Leptospirosis

Leptospirosis is a bacterial zoonotic disease that affects humans and animals, most often occurring in tropical or subtropical regions.

While most infected individuals do not show any signs or symptoms, the bacterial disease can cause a wide range of symptoms, similar to other water-borne diseases but also including fever, chills, headache, jaundice, and red eyes.

Without treatment the disease can lead to kidney damage, meningitis, liver failure, and respiratory distress.

Leptospira is spread through the urine of infected animals and is associated with recreational water sports that take place in contaminated lakes and rivers.

Salmonella

Salmonellosis is a bacterial infection that is usually caused by eating foods contaminated with animal feces. The bacteria can also contaminate water.

These are often foods from animals, such as beef, poultry, milk, or eggs; however, any food may become contaminated. Food may also become contaminated if an infected food handler fails to wash their hands with soap after using the bathroom. Additionally, Salmonella can also be found in pet feces, particularly reptiles and young birds.

Always wash your hands immediately after handling animals and also after contact with raw meat or poultry. Other prevention methods include cooking poultry, beef, and eggs thoroughly and not consuming foods containing raw eggs, or raw (unpasteurized) milk.

E. coli
E. coli are a large and diverse group of bacteria. While most strains are harmless, others can make you sick with diarrhea, stomach cramps, and vomiting. Symptoms are usually resolved within 5–7 days.

E. coli infections can be prevented by thoroughly washing hands after using the bathroom, after changing diapers and before preparing or eating food.