Private drinking water wells and contamination

It’s unclear exactly how many Americans rely on private wells for their drinking water. But most estimates put it at about 44 million people — nearly 14 percent of the U.S. population.

Although federal and state governments oversee the quality of tap water provided by public water systems, private well owners have to monitor and maintain their water supply.

Some states and local governments have rules for the construction, placement and testing of new private wells. But very few places have laws about how wells should be handled after they’re in place. So once a well has been dug, its owners are largely responsible for protecting, maintaining, testing and treating it.

Common well contaminants

Wells pull water from the ground, as opposed to surface water like rivers and streams. Some well contaminants are naturally found in groundwater and surrounding mineral deposits. These include:

• Radioactive elements such as radium and uranium. Health effects from these substances can vary, but all radioactive elements increase the risk of cancer. They may also damage the nervous, immune and endocrine systems.
• Metals. Some metals that can naturally occur in groundwater are arsenic, manganese and iron. People who drink water contaminated with arsenic could face an increased risk of bladder, lung and skin cancer. Arsenic has also been linked to liver, kidney and prostate cancers and to cardiovascular disease. As a tap water contaminant, manganese is linked to developmental issues in children. While typically not harmful to health, high levels of iron can cause issues with taste and staining laundry. (See more about metals below.)
• Fluoride. Occurs naturally in groundwater, and it’s also added to drinking water by many water systems to help prevent tooth decay. But exposure to high levels of fluoride can cause tooth and bone damage in young children, neurodevelopmental problems and may increase the risk of osteosarcoma, a type of bone cancer.
• Nitrate. Can occur naturally in groundwater at low levels. But when it’s found at or above 3 milligrams per liter, it’s generally considered to be a result of human activity. (See more about this contaminant below.)

Private well contamination also frequently originates from human activities, including:

• Metals. Lead and copper can leach from pipes and plumbing fixtures – especially in homes built before 1986. Both metals are linked to serious developmental issues in exposed children.
• Nitrate. Although nitrate is naturally found in soil at low levels, higher levels in tap water are often a result of fertilizer runoff from farm fields. Other, less common sources of nitrate contamination of private wells are urban stormwater runoff, discharge from municipal wastewater treatment plants and leaking septic tanks. Tap water contaminated with nitrate is linked to increased cancer risk and harm to the developing fetus. Infants and children exposed to high levels of nitrate in tap water are at risk of oxygen deprivation in blood.
• Pesticides. Toxic pesticides like atrazine often migrate into groundwater in agricultural areas. Atrazine disrupts the human hormone system.
• Industrial products and wastes. Can contaminate groundwater through improper disposal, leaks from underground tanks and migration from landfills or waste dumps. Problematic chemicals include carcinogenic volatile organic compounds, which are linked to several kinds of cancer and other serious health problems like harm to the liver, kidneys and nervous system.
• Bacteria and other pathogens. Bacteria, viruses and other parasites can contaminate wells from both natural and human-related activities. They can be particularly prevalent in agriculture-heavy areas. Some especially concerning contaminants include giardia, salmonella, E. coli and cryptosporidium. People who drink water with one or more of these pathogens can experience severe acute gastrointestinal illnesses, catch long-term infections or even die. Boiling water to kill microbes offers an immediate remedy to microbial contamination. But in the long term, the only effective solutions are finding a new source of water, building a new well or requiring polluters to prevent runoff of manure and other contaminants.

Testing your well

It’s a good idea to conduct regular tests of your well, because contaminant levels can change over time. The Centers for Disease Control and Prevention recommends testing every spring.

You should also test your well:

• Before you use it for the first time.
• If someone in your household is pregnant or nursing.
• If there are known problems with well water in your area.
• If your household plumbing contains lead.
• If there has been recent flooding in your area.
• After you repair any part of your well system.
• If you notice changes in the taste, color or odor of your water.
• If anyone in your household has had a gastrointestinal disease.

For accurate information about contaminants, private wells should be tested by a laboratory certified to test drinking water. The Environmental Protection Agency provides information about certified labs in each state.

Local health departments may also have programs to test private well water, or to assist with the costs of testing.

Addressing well contamination

Private well owners should contact their local or state health department for more information and to discuss the results of well testing.

In-home water treatment may be recommended to remove some chemicals, but different types of devices remove different pollutants.

Practice regular maintenance of your well. Look each month for cracking, corrosion or a missing well cap. Keep records of testing and maintenance.

Hire a certified well driller for any new construction or modifications.

After a flood, get your well professionally inspected and cleaned. Do not turn on the pump until after it has been inspected.

To prevent contamination, identify potential sources near your well, such as livestock operations, septic tanks or fuel spills.

Additional private well resources

The EPA’s list of state resources and programs:
www.epa.gov/privatewells/private-drinking-water-well-programs-your-state

The CDC’s “Guide to Drinking Water Treatment Technologies for Household Use”:
https://www.cdc.gov/healthywater/drinking/home-water-treatment/household_water_treatment.html