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Well Water Testing

Properly constructed and maintained water wells can provide many years of trouble-free service, but wells can eventually deteriorate or become damaged and allow surface contaminants to enter the water. In addition, some groundwater can contain one or more chemical substances in levels above health-based standards. In some cases, contamination of the water can be detected by sight, taste or smell; however, many of the most serious problems can only be detected through laboratory testing of the water.

Public water systems are tested regularly for a variety of contaminants. However, if you have a private well, regular testing is your responsibility. Well construction inspection and improvements, such as fixing a crack in a casing, are important steps in keeping your well water safe.

A homeowner sampling for VOC's from a faucet.

Public water systems are tested regularly for a variety of contaminants. However, if you have a private well, regular testing is your responsibility. Well construction inspection and improvements, such as fixing a crack in a casing, are important steps in keeping your well water safe.

The information on this page is also available in the Testing Private Well Water brochure produced jointly by the Illinois EPA and the Illinois Department of Public Health.

Here are some recommendations that you can follow to help ensure that your well water is safe:

Test your well water at least once a year for bacteria

Water that has become contaminated by human or animal waste can transmit a variety of infectious diseases, including dysentery, salmonellosis, hepatitis, and giardiasis. Symptoms vary, but nausea, vomiting, and diarrhea, with or without fever, are most common. To assess bacterial safety, drinking water is tested for a group of "indicator bacteria" called coliform bacteria. These bacteria do not usually cause disease themselves, but their presence indicates that surface contamination has found its way into the well and disease organisms may also be present. When coliform bacteria are found in well water, the water should be boiled before being used for drinking or cooking, and the well should be disinfected. In cases when bacteria problems cannot be solved, then you may want to look into continuous chlorination treatment.

Test your well water every year for nitrate, and always test the water for nitrate before giving it to an infant

Nitrate is a common contaminant in Illinois groundwater. An elevated level of nitrate is often caused by septic systems, manure storage areas, feedlots, or farm fields near the well. Wells vulnerable to nitrate contamination include shallow sand point wells and large diameter dug or bored wells and wells with damaged, leaking casing or fittings. Well water containing nitrate at levels above the maximum contaminant level established by the U.S. Environmental Protection Agency (EPA), which is 10 milligrams per liter as nitrogen, should never be given to infants less than 6 months old because it can cause a potentially fatal disease called "blue baby syndrome." In many cases, constructing a deeper well can reduce or eliminate a nitrate problem. If you know, or suspect, that your well water may contain high levels of nitrate, do not boil the water, as this will only concentrate nitrate levels. If nitrates cannot be eliminated from your well water then you may need to look into reverse-osmosis or distillation treatments.

Testing your well water for other contaminants


Volatile organic chemicals, or "VOCs," are common components of gasoline and other fuels, as well as paints, and solvents, such as cleaners and degreasers. The Target List of VOCs and their standards contains information on what to test for and what the acceptable levels are. Long-term exposure to VOCs at levels greater than drinking water standards may lead to impaired immune system function, may cause liver damage or may increase the risk of cancer. If you live in an urban or suburban area with a business, industry or gas station nearby, the Illinois EPA and IDPH recommend that you have your water tested for VOCs. Also, wells in rural areas that may be affected by leaking fuel tanks should test for VOCs. See the general procedures for collecting water samples for VOC testing fact sheet for more information. ( Procedimiento general para recoger muestras de agua para hacerles la prueba de químicos orgánicos volátiles)


Research by state and federal agencies in Illinois shows a low potential for finding pesticides above levels of concern in groundwater as a result of normal use on farm fields. However, if pesticides have been mixed, loaded or stored close to your well and you have a sand point well or a large diameter dug or bored well, you should consult with your local health department to find out whether you should test for those pesticides. Long term exposure to some pesticides at levels above health standards may cause a variety of health effects, including damage to the liver, kidneys, adrenal gland or nervous systems. You may also contact your local University of Illinois Extension office for more information on pesticide use.


This naturally occurring radioactive element is found primarily in the northern third of Illinois within the deep rocks, soil and groundwater. Radium has been detected in private wells and can only be identified through testing of the water. Long term exposure to radium at levels above health standards may increase the risk of bone cancer, leukemia, aplastic anemia and lymphoma.

There are other potential contaminants for which you may want to test your well water.

Flush standing water to reduce levels of lead.

Well water in Illinois rarely contains detectable levels of lead. However, lead can enter drinking water through decay of plumbing materials. Homes built before 1986 are more likely to have lead pipes, fixtures and solder. However, new homes are also at risk: even legally "lead-free" plumbing may contain up to 8 percent lead. The most common problem is with brass or chrome-plated brass faucets and fixtures. Exposure to lead at levels above health standards can impair a child's development, as well as cause a variety of other adverse health effects in both children and adults.

To minimize your exposure to lead in drinking water, run the water until it gets cold before using it for drinking or cooking. This will flush out most of the lead that may have accumulated in the plumbing. Also, never use water from the hot water tap for drinking or cooking. Hot water is likely to contain higher levels of lead. The only way to be sure of the amount of lead in your household water is to have it tested by a certified laboratory.

Who can I contact to have my well water tested?

Coliform bacteria and nitrates should be tested on a yearly basis and can be done by most local health departments. To find your local county health department, visit the Illinois Department of Public Health's alphabetical listing of Local Health Departments. You can also locate your local health department by county on their online regional map. Certified labs also test well water and may be your only option for certain chemicals. Consult with your local health department to see if you should be testing for other contaminants (e.g., metals, VOCs, SVOCs, etc) and the frequency of testing.

For More Information

For more information about water quality testing for private wells, including information about contacting certified labs in Illinois, contact your local health department; the Illinois Department of Public Health at (217) 782-5830 or visit these links: