Water Testing

The National Ground Water Association (NGWA) recommends well owners test their water at least annually for bacteria, nitrates, and any contaminants of local concern.

Check with your local health or environmental health department for recommendations regarding the type and frequency of testing specific to your location.

Water testing questions:

Why is it important to test annually for bacteria and nitrate?
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Bacteria is present throughout the environment. Consequently, a well system that is not properly sealed off from outside bacteria can be vulnerable. Wells also can be vulnerable if there is an overloading of the groundwater with bacteria, for instance from an animal enclosure or a septic system failure.

While many forms of bacteria are not harmful, some are pathogenic, meaning they cause disease, such as E. coli. Pathogenic bacteria can cause moderate to severe gastrointestinal illness or even death. Typically, well water is sampled first for coliform bacteria, which is not harmful. A test that is positive for coliform bacteria indicates that the conditions exist in the well to support other types of bacteria, including pathogenic bacteria.

Nitrate is common in rural areas, which tend to rely more on water wells for household drinking water. Nitrate is often used in fertilizer, and it also is a byproduct of animal and human waste. The greatest danger from nitrate is its ability to inhibit the blood’s capacity to carry oxygen in infants under the age of about six months. This condition is called methemoglobinemia, commonly known as “blue baby syndrome.”

Learn more about water testing here.

How do I know if I have dangerous bacteria or nitrate in my well water?


If your water tests positive for coliform bacteria, it means the conditions exist in your well to support other bacteria, including harmful disease-causing (pathogenic) bacteria. Consult with your drinking water testing laboratory about doing further testing for pathogenic bacteria.

The Maximum Contaminant Level for nitrate in water from public water systems is 10 parts per million. Remember, this is a health threat to infants under the age of about six months who may be drinking formula made with nitrate-contaminated well water.

To learn more about interpreting water test results, click here.

Can there be contaminants locally? If so, for what should I test?

Yes, there can be localized contamination. Such contamination can occur naturally in the geology, such as arsenic or radon. Other local contaminants may be manmade, for instance, toxic substances from former industrial sites, landfills, or chemical spills.

To learn what might be of local concern, start with your county health or environmental health department. Many county health departments provide some water testing and may know about localized groundwater contaminants.

You also can check with drinking water testing laboratories that serve your area to find out about localized groundwater contamination threats.

Learn more about water testing here.

How do I find a drinking water testing laboratory?

You can start by checking with your health or environmental health department at the county or state levels. These departments often do some water testing. You also can click here: “Find a Certified Testing Lab.”

How much does a water test cost?

It depends. Some contaminants are more or less difficult to test and therefore more or less expensive. Also, the number of substances being tested can affect the price significantly. Consequently, depending on the type and number of tests you want, the cost could be from under $50 to hundreds of dollars or more. Often if the well owner tests for bacteria, nitrate, and anything of local concern, this will amount to a handful of tests. Some laboratories provide packages that cover different ranges of testing. To decide on your testing needs, get the advice of your water well system professional, local health department, or a drinking water testing laboratory.

You also can click here: “Find a Certified Testing Lab.”

How are water samples taken, and who takes them?

Drinking water testing laboratories or local governments that offer water testing often provide a test kit to the well owner. The test kit will have everything the well owner needs to take a sample.

Testing kits have instructions on precisely how to take the sample. This can be very important, since some sample collection requires very careful handling—for instance, in the case of bacteria. Great care must be taken to properly disinfect the faucet or spigot and to not inadvertently introduce bacteria into the sample by touching the lip or inside of the bottle—or allowing anything to touch the inside of the lid.

Some types of samples must be processed by a lab within a certain time or be kept at a certain temperature. The sample collection instructions should make these details clear. When in doubt, ask the lab or the testing program.

The testing of other substances may be comparatively simple.

Some labs or testing programs will do the sampling for the well owner, but many if not most do not. You also can click here: “Find a Certified Testing Lab.”

How often should I test my water?

It depends.

The National Ground Water Association recommends that well owners test annually for bacteria and nitrate, though organizations may differ on their recommendations.

Changing circumstances might warrant water testing at more frequent intervals. Three examples are (1) a sudden change in one’s water quality, (2) the occurrence of a nearby chemical spill, or (3) contamination that is spreading in groundwater over time and approaching nearby wells. Conversely, some contaminants, once discovered, may not need to be tested again because they exist naturally in the geology and groundwater and will always be present. Anytime there is a change in your water’s taste, odor, or appearance—or a noticeable decrease of water flow into your well—you should test your water. Discuss the symptoms to your water well system professional or a drinking water testing laboratory for recommendations on what to test.

Sudden changes in water quality could signal that the well needs to be cleaned or that surface water is infiltrating the well through a breach in the well system. Well maintenance often can restore water quality to previous conditions. Learn more about water testing here.

Should I test water from my water treatment system periodically?

Yes. First, check the water treatment system owner’s manual for recommendations on water testing. If you do not have that information, contact the manufacturer or go online to see if you can find the maintenance information for your product’s make and model.

Generally, treated water should be tested after the treatment system is installed to make sure it is working. You also can test the water after the treatment system is serviced to make sure it is working properly. Another reason to test is if the treatment system has not been maintained according to the product maintenance recommendations. Neglecting maintenance such as the timely replacement or cleaning of a filter could impair the treatment system’s effectiveness.

Will my water test results show me if I have a water quality problem and how to fix it?
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Drinking water testing labs vary in the degree to which they explain test results and give guidance on what to do if there is a problem. Some labs provide a simple explanation of results and suggest appropriate treatment technologies if there is a problem. Other labs provide numerical results of contaminant levels with little explanation or guidance.

If the lab does not interpret the results or provide next steps for the well owner, consider showing your results to your water well system professional—or talk with someone at your county health or environmental health department.

Another option is to use a water test interpretation tool online. There are a number of such tools available.

Lab test results are very important if you are considering getting a water treatment system. You should always compare your water test results against the specifications of the treatment system you are considering. This should tell you whether the system is designed to treat what you need to treat in the concentration at which it exists in your water.

Learn more about water testing here.

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