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Private Wells and Water-Related Diseases

Bacteria and Parasites

An estimated 20 percent of the population in New Mexico gets their drinking water from private wells. The water quality of a private well is unregulated in the state of New Mexico; therefore, well owners are the best protection of their water supply.

Well owners are responsible for testing their water (for bacteria and chemicals), treating (when applicable) and protecting their water supply (learn more about private well resources).
Naturally present bacteria in the aquifer (groundwater) environment Information
Coliforms Widely present in the environment. Most strains will not make you sick. Coliforms are tested in drinking water as an indicator for other potentially harmful organisms such as E. coli.
Sulfur bacteria Hydrogen Sulfide and Sulfur bacteria can be present in low oxygen water (such as deep wells). Sulfur bacteria produce hydrogen sulfide gas and a rotten egg smell. While unpleasant, the concentrations in private drinking water supplies are typically found below levels that would cause health concerns.
Iron bacteria This bacterium forms a smelly biofilm that thrives when iron is present. These naturally occurring biofilms are usually harmless. Iron can change how the water looks and tastes.


Enteric (Intestinal) Illness Causing Organisms
Bacteria Parasites Viruses
Shigella
Shigella
Giardia
Giardia
Rotavirus
Rotavirus
Examples Escherichia coli Giardia Enterovirus
Campylobacter Norovirus
Salmonella Rotavirus
Shigella Hepatitis A
Cryptosporidium
How do they get into drinking water (wells)? The well water gets contaminated with infected human or animal waste. Common sources are: septic systems, animals such as livestock, and fertilizer (manure). The well can become contaminated after maintenance or a disturbance (like a flood) if the well head is damaged or not properly maintained.
What kind of illness do they cause? Gastro-intestinal problems. Common symptoms include: Stomach cramps or pain, diarrhea (sometimes bloody), vomiting, fever, rotten egg smelling diarrhea (giardia).
What can I do?
  • Protect your water source from waterborne pathogens.
  • Treat your water.
  • Clean your well.
  • Boil water (if well water has tested positive for bacteria)
  • Prepare when flooding is likely.
  • Consider an alternative clean water source for drinking, cooking and bathing.
  • See a health care provider for any health concerns
Susceptible populations Children, the elderly and immune-compromised people.


Some microorganisms are naturally present in the environment and do not represent a health risk. Other organisms including bacteria, parasites and viruses are associated with human or animal waste and can get into groundwater (well water) and cause illness. The most common type of illness experienced is gastrointestinal with symptoms such as: stomach cramps or pain, diarrhea (sometimes bloody), vomiting, and fever. Depending on the organism, symptoms can last from 5 days to 6 weeks.

For any health concerns, contact your healthcare provider. For questions about waterborne diseases, you can contact the Epidemiology and Response Division on-call number to speak with an epidemiologist at (505) 827-0006 or 888-878-8992.

According to the Centers for Disease Control and Prevention (CDC), the top 5 causes of outbreaks in private water systems (wells) are infectious diseases. These include:

Top Causes of Outbreaks in Wells 1971-2010
1. Hepatitis A
2. Giardia
3. Campylobacter and E. coli (tie)
4. Shigella
5. Cryptosporidium and Salmonella (tie)

Learn more about water-related diseases in private wells from the CDC.
Children and the elderly and immune-compromised people can be more susceptible to waterborne pathogens. Dehydration can result from diarrhea or vomiting. If contamination is known or suspected, use an alternate clean water source for bathing and drinking. If any possible symptoms of dehydration, vomiting or weight loss occur, visit your healthcare provider.

Children may drink water frequently and therefore be more susceptible to waterborne illness. Supervise children's hand washing and bathing to limit potential exposure.
Test your well water!
  • Test your water annually for bacteria - spring is best!
  • Test after any changes- flooding or other land disturbances, well maintenance, changes in water level or quality (smell, taste or color change).
  • Test for a newly purchased home or a newly rented residence.
  • Bacteria is best analyzed in a clean environment like a laboratory, where cross contamination can be minimized. Find a certified lab.
  • The water quality can affect what kind of treatment is appropriate. At a minimum test your water:
    • Annually:
      Fecal coliform bacteria (including E. coli)
      Nitrate
    • At least once:
      Nitrite
      Arsenic
      Uranium
      Lead
      Fluoride
  • Learn more about how and where to test your water.
Some microorganisms can be naturally present in the groundwater environment.

The only way to know if waterborne disease-causing microorganisms (pathogens) are in the water is to test it.

Protect your well water

Disease causing microorganisms can get into the water when it is contaminated with feces from infected animals or people. Contamination can occur from various sources such as:

Nearby septic systems. Learn more about groundwater protection and your septic system.

Proximity of animals such as livestock.

Proximity of animal waste such as manure.

Contamination after flooding.
Waterborne Organisms and Private Wells

Maintain a safe distance between private wells and possible sources of contamination.

  • Protect your water source from waterborne pathogens:
    • Keep possible contaminant sources a safe distance from any well. If you live in an area with a high density of private wells, you can be a good steward by not disposing of manure and chemicals on your property and by keeping possible contaminant sources on your property a good distance from the well head on your neighbor's property.
    • Make sure your well has a sanitary cap or seal.
    • Make sure the ground is sloped away from the well so water flows away from the well head.
    • Make sure the casing extends 18 inches above the land surface (NMAC 19.27.4).
  • Prepare when flooding is likely:
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Content updated: Sat, 27 Apr 2019 13:55:07 MDT