Private drinking water wells
About 44 million Americans — nearly 14 percent of the U.S. population — rely on private wells for their drinking water. Whereas federal and state governments have authority over water quality from public water systems, private well owners are on their own. Some states and local governments have rules for the construction and placement of new wells, but private well owners are largely responsible for protecting and maintaining their wells and testing their water.
Should I be worried about contamination in my well?
The U.S. Geological Survey studied water quality in thousands of private domestic wells and reported that almost one-fourth contained at least one contaminant at levels that raise health concerns because of the presence of radioactive substances, metals or fluoride. Contaminants related to agriculture, such as nitrate, can also harm water quality in private wells.
What contaminants are a concern in private wells? What are their health effects?
Substances found in groundwater and surrounding mineral deposits include:
- Radioactive elements such as radium or uranium. Different types of radioactive elements are associated with different health effects, but all of them increase the risk of cancer. The latest research also finds that radioactive substances may damage the nervous, immune and endocrine systems.
- Metals. Arsenic is commonly found in groundwater, particularly in the West, Midwest and Northeast. The USGS found nearly 7 percent of private wells across the country have levels of this known carcinogen above legal limits.
- Fluoride occurs naturally in surface and groundwater, and is also added to drinking water by many water systems. In 2015, the U.S. Public Health Service recommended no more than 0.7 milligrams of fluoride per liter of water. Exposure to high levels of fluoride causes tooth and bone damage in young children, and may increase the risk of osteosarcoma, a type of bone cancer.
Groundwater contaminants from human sources include:
- Nitrate, a fertilizer chemical, frequently contaminates drinking water due to agricultural and urban runoff. Discharge from municipal wastewater treatment plants and leaking septic tanks is another source of nitrate contamination. Infants and children are at risk of oxygen deprivation in blood when exposed to high levels of nitrate in drinking water. Nitrate is also linked to the increased risk of cancer and harm to the developing fetus.
- Toxic pesticides commonly migrate into groundwater in agricultural areas.
- Industrial products and wastes can contaminate groundwater through improper disposal, leaks from underground tanks, and migration from landfills or waste dumps. Carcinogenic volatile organic compounds, or VOCs, can pollute private water wells near industrial sites or landfills.
- Lead and copper can leach from pipes and plumbing fixtures because of the presence of corrosive compounds such as acids in groundwater. Homes built before 1986 are more likely to have lead pipes. If your water has a pH value of less than 7, or other indicators of corrosive water, metals such as copper and lead can easily leach from pipes into water. To address this issue, private well owners can install a treatment system to balance the water’s chemistry.
- Microbes such as bacteria, viruses and other parasites can contaminate wells from both natural and human-related activities. Water contaminated with infectious microbes can cause gastrointestinal illnesses, and in more severe cases, long-term infections may follow. This concern particularly affects private well owners who live near large animal feeding operations. 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 the polluters to prevent runoff of manure and other contaminants.
How can I find out what contaminants are in my well?
The only way is to have it tested by a certified laboratory.
When should I have my water tested and who should test it?
The Centers for Disease Control and Prevention recommends regular mechanical maintenance and tests every spring. Regular tests are recommended because contaminant levels can change over time. You should also test your well:
- Before you use it for the first time.
- If someone in the 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 flooding or other land disturbances 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.
Contact a laboratory that is 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.
What can a well owner do if contaminants are detected?
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.
How can I keep my well safe?
- Get it tested annually. You don’t know what’s in the water if you don’t test.
- Stay vigilant and identify potential sources of contamination near your well, such as livestock operations, septic tanks or fuel spills.
- 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.
Where can I find additional resources?
The EPA’s list of state resources and programs:
The EPA’s factsheet “Drinking Water From Household Wells”:
The CDC’s “Guide to Drinking Water Treatment Technologies for Household Use”: