Using Private Wells: A Drinking Water Safety Guide

Nearly one in seven Americans get their drinking water from private wells. Federal and state governments set legal limits for contaminants in public water systems, but those laws don't cover private wells. If you're one of the 44 million people relying on a private well for drinking water, here's what you should know and do to make sure your water is safe.

Should I be worried about contamination in my well?

In 2009 the U.S. Geological Survey released a report based on studies of thousands of private domestic wells, finding that almost one-fourth contained contaminants – such as radioactive substances, metals or fluoride – at potentially harmful levels. Agricultural chemicals, such as fertilizer and pesticides, can also harm the groundwater that supplies most private wells. Public systems are required to treat water to lower the level of regulated contaminants, but private well owners are on their own.

Shouldn’t the government require testing of private wells?

Some states and localities require private well owners to test for arsenic or other contaminants during home construction and real estate deals. But there is no nationwide requirement for well owners to test their water. Well owners may not know their groundwater could be contaminated or how to test it. They may think it's too expensive or just not think water contamination is anything to worry about.

A recent analysis in the journal Environmental Health Perspectives called for universal testing for drinking water contaminants in well water. Researchers said states should require testing on new homes and for real estate deals that include private wells to raise awareness and community engagement on groundwater contamination. They also called for subsidies to help lower-income communities and well owners meet the cost of testing.

What contaminants are a concern in private wells? What are the 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, a known carcinogen, is commonly found in groundwater, particularly in the West, Midwest and Northeast. The U.S. Geological Survey found that nearly 7 percent of private wells across the country have levels of arsenic above legal limits.
Fluoride. It occurs naturally in surface water and groundwater, and many public systems also add it to tap water. In 2015, the 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 risk of osteosarcoma, a type of bone cancer. The Centers for Disease Control and Prevention state that if infant formula is mixed with water containing fluoride, the baby’s teeth might be affected by dental fluorosis, which appears as white spot markings on the teeth.

Groundwater contaminants from human sources include:

Nitrate, a fertilizer chemical, which frequently contaminates drinking water due to agricultural and urban runoff, and discharges from municipal wastewater treatment plants and septic tanks. Infants and children exposed to high levels of nitrate in drinking water may not get enough oxygen in their blood. Nitrate is also linked to increased risk of cancer and harm to developing fetuses.
Toxic pesticides, which commonly migrate into groundwater in agricultural areas.
Industrial products and wastes, which can contaminate groundwater from improper disposal, leaks from underground tanks, or leaching from landfills or waste dumps. Carcinogenic volatile organic compounds, or VOCs, can pollute private water wells near industrial sites or landfills.
Lead and copper, which can leach from pipes and plumbing fixtures due to 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 has other indicators of corrosive water, metals such as copper and lead can easily leach from pipes into water. To address this problem, private well owners can install a treatment system to balance the water’s chemistry.
Microbes such as bacteria, viruses and other parasites, which 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 particularly affects private well owners who live near large animal feeding operations. Boiling water to kill microbes offers an immediate remedy, 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.

How can I find out what contaminants are in my well?

The only way is to have it tested by a certified laboratory. This Environmental Protection Agency website will help you find a certified lab in your state. Local health departments may also have programs to test private well water.

When should I have my water tested?

The Centers for Disease Control and Prevention recommend regular mechanical maintenance and testing your well every spring. Regular testing is 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 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 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.

What should I do if contaminants are detected?

Contact your local or state health department for more information and to discuss the test results. You can also compare your results to EWG’s Drinking Water Standards, which reflect the best and most current science about health risks of contaminants, instead of government regulations that are often based on political and economic compromises or outdated studies. In-home water treatment will remove some chemicals, but different types of devices remove different pollutants.

How can I keep my well safe?

Have it tested annually. You don’t know what’s in the water if you don’t test.
Remain aware of 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, have your well inspected and cleaned by a professional. Do not turn on the pump until after inspection.

Where can I find additional resources?