Germs That Can Contaminate Tap Water
Find out if your tap water is contaminated
If you suspect your tap water has harmful germs or chemicals in it, contact your drinking water utility. If you have a private well, contact your local health department for help with water testing. Consider using bottled water for drinking and cooking until the problem is resolved.
Some germs can make you sick if they are in your tap water. Find information below about the germs that most often contaminate tap water and cause disease, and how to remove or control them.
Cryptosporidium (Crypto)
- Common sources: Feces (poop) from infected people or animals that gets into the water through sewage overflows, sewage systems that are not working properly, polluted storm water runoff, or agricultural runoff
- Removing it from drinking water: Boil your water for 1 minute (at elevations above 6,500 feet, boil for 3 minutes), use a filter certified to remove Crypto, or treat water using reverse osmosis, UV light, or ozone.
- Illness: The most common symptom is watery diarrhea. Learn more.
Campylobacter
- Common sources: Poop from infected people or animals that gets into the water from sewage overflows, sewage systems that are not working properly, polluted storm water runoff, or agricultural runoff
- Removing it from drinking water: Boil your water for 1 minute (at elevations above 6,500 feet, boil for 3 minutes) or disinfect it using chemicals. Specially designed filters and other water treatment technologies might also be effective.
- Illness: Common symptoms include diarrhea, fever, and stomach cramps. Learn more.
E. coli O157
- Common sources: Cattle farms, where E. coli O157 can live in the intestines of healthy cattle; less commonly, poop from an infected person or animal that gets into the water through sewage overflows, sewage systems that are not working properly, polluted storm water runoff, or agricultural runoff
- Removing it from drinking water: Boil your water for 1 minute (at elevations above 6,500 feet, boil for 3 minutes) or disinfect it using chemicals. Specially designed filters and other water treatment technologies might also be effective.
- Illness: Common symptoms include severe stomach cramps, diarrhea (often bloody), and vomiting. Learn more.
Enterovirus
- Common sources: Poop from infected people that gets into the water from sewage overflows, sewage systems that are not working properly, or polluted storm water runoff
- Removing it from drinking water: Boil your water for 1 minute (at elevations above 6,500 feet, boil for 3 minutes). Disinfectants don’t work well to kill enteroviruses and enteroviruses are too small to be removed by home or camping water filters.
- Illness: Symptoms are often mild and commonly include fever, runny nose, sneezing, cough, skin rash, mouth blisters, or body and muscle aches. Learn more.
Giardia
- Common sources: Poop from infected people or animals that gets into the water from sewage overflows, sewage systems that are not working properly, polluted storm water runoff, or agricultural runoff
- Removing it from drinking water: Boil your water for 1 minute (at elevations above 6,500 feet, boil for 3 minutes), use a filter certified to remove Giardia or Cryptosporidium cysts, or treat water using reverse osmosis, UV light, or ozone.
- Illness: Common symptoms include diarrhea, gas, greasy stools (poop), stomach cramps or pain, upset stomach, nausea, vomiting, or dehydration (loss of fluids). Learn more.
Hepatitis A virus
- Common sources: Poop from infected people that gets into the water from sewage overflows, sewage systems that are not working properly, polluted storm water runoff, or agricultural runoff
- Removing it from drinking water: Boil your water for 1 minute (at elevations above 6,500 feet, boil for 3 minutes) or disinfect it using chemicals. Hepatitis A virus is too small to be removed by home or camping water filters.
- Illness: Symptoms can include yellow skin or eyes, loss of appetite, upset stomach, throwing up, stomach pain, fever, dark urine or light-colored stools (poop), diarrhea, joint pain, or feeling tired. Learn more.
Legionella
- Common sources: Legionella bacteria are found naturally in freshwater environments, like lakes and streams. The bacteria can become a health concern when they grow and spread in building water systems, such as faucets or hot water heaters, and devices that create small droplets of water, such as cooling towers, hot tubs, or decorative fountains. Most identified outbreaks are in buildings with large, complex water systems, such as hotels, long-term care facilities, and hospitals.
- Removing it from drinking water: To control the growth and spread of Legionella in building water systems, owners and managers should maintain water systems and implement a water management program with Legionella control measures. You can also take steps at home to reduce the growth and spread of Legionella and other germs in your faucets, showerheads, hot water heater, and other water devices like hot tubs [PDF – 1 page].
- Illness: Symptoms can include cough, shortness of breath, fever, muscle aches, or headaches. Learn more.
Norovirus
- Common sources: Poop from infected people that gets into the water from sewage overflows, sewage systems that are not working properly, or polluted storm water runoff
- Removing it from drinking water: Boil your water for 1 minute (at elevations above 6,500 feet, boil for 3 minutes). Noroviruses are moderately resistant to chlorination, so check with your health department about disinfection. Noroviruses are too small to be removed by home or camping water filters.
- Illness: Common symptoms include diarrhea, vomiting, nausea, or stomach pain. Learn more.
Rotavirus
- Common sources: Poop from infected people that gets into the water from sewage overflows, sewage systems that are not working properly, or polluted storm water runoff
- Removing it from drinking water: Boil your water for 1 minute (at elevations above 6,500 feet, boil for 3 minutes) or disinfect it using chemicals. Rotavirus is too small to be removed by home or camping water filters.
- Illness: Common symptoms include severe watery diarrhea, vomiting, fever, or abdominal pain. Learn more.
Salmonella
- Common sources: Poop from infected people or animals that gets into the water from sewage overflows, sewage systems that are not working properly, polluted storm water runoff, or agricultural runoff
- Removing it from drinking water: Boil your water for 1 minute (at elevations above 6,500 feet, boil for 3 minutes) or disinfect it using chemicals. Specially designed filters and other water treatment technologies might also be effective.
- Illness: Common symptoms include diarrhea (that can be bloody), fever, and stomach cramps. Learn more.
Shigella
- Common sources: Poop from infected people that gets into the water from sewage overflows, sewage systems that are not working properly, or polluted storm water runoff
- Removing it from drinking water: Boil your water for 1 minute (at elevations above 6,500 feet, boil for 3 minutes) or disinfect it using chemicals. Specially designed filters and other water treatment technologies might also be effective.
- Illness: Common symptoms include diarrhea (that can be bloody), fever, stomach pain, or feeling the need to poop even when bowels are empty. Learn more.
Report Waterborne Illnesses
If you think you or someone you know got sick from water, please report it to your local health department. Report it even if you don’t know what made you sick. Reporting an illness can help public health officials identify a waterborne disease outbreak and keep others from getting sick.
Page last reviewed: August 23, 2022