PFAS in Private Wells: Testing and Treatment

Last updated: April 2026

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Quick Answer

Private well owners are responsible for testing their water at least once every year for total coliform bacteria, nitrates, total dissolved solids, and pH level CDC Guidelines for Testing Well Water.
The U.S. Environmental Protection Agency's (EPA) rules that protect public drinking water systems do not apply to privately owned wells CDC Guidelines for Testing Well Water.
If your well water tests positive for total coliforms, retest for fecal coliforms or E. coli to confirm contamination What to do About Coliform Bacteria in Well Water.
Many coliforms are harmless, but fecal coliforms like E. coli can make people sick with symptoms that include diarrhea, cramps, nausea, and headaches, and can even lead to kidney failure Positive Coliform Test - What you need to know.

As a private well owner, you carry the full responsibility for making sure your drinking water is safe. Unlike public water systems, private wells are not regulated by the U.S. Environmental Protection Agency (EPA), meaning no government official monitors, treats, or oversees your tap water CDC Guidelines for Testing Well Water. This makes regular testing crucial. We recommend testing your well water at least once every year for total coliform bacteria, nitrates, total dissolved solids, and pH level. If tests show contamination, especially from fecal coliforms or E. coli, it indicates contact with human or animal waste and could cause illness.

Why is Testing Your Private Well Water So Important?

Testing your private well water is important because you, as the well owner, are solely responsible for its safety. Government officials do not regulate, treat, or monitor the tap water from private wells, unlike public drinking water systems CDC Guidelines for Testing Well Water. This means the burden of ensuring your water is safe for drinking, cooking, and bathing falls entirely on you. Without regular testing, you could be unknowingly consuming water contaminated with harmful germs or chemicals that can lead to serious health issues for you and your family.

The Owner's Responsibility

When you own a private well, you become the primary steward of your water supply. This responsibility extends beyond just maintaining the well structure. It involves understanding the potential risks to your water quality and actively taking steps to mitigate those risks. The U.S. Environmental Protection Agency (EPA) has strict rules for public drinking water systems, but these rules do not apply to privately owned wells. This critical distinction means that while a city water supply undergoes regular, mandated testing and treatment, your private well does not. The local government may offer assistance in getting your well water tested, but the initiative and follow-through remain yours.

Unseen Dangers in Well Water

Many contaminants in well water are invisible, odorless, and tasteless. This makes them impossible to detect without proper laboratory testing. For example, total coliform bacteria, a key indicator of potential contamination, can enter your well water without any noticeable change in the water's appearance or smell. While many coliforms are harmless, their presence suggests that a pathway exists for disease-causing microorganisms, such as certain viruses, bacteria, and parasites, to enter your water supply. These harmful germs can cause a range of illnesses, from mild gastrointestinal upset to severe, life-threatening conditions.

Chemical contaminants, such as nitrates, are another silent threat. Nitrates can originate from fertilizers, septic systems, and animal waste, and high levels can be particularly dangerous for infants, leading to a condition known as "blue baby syndrome." Testing for total dissolved solids (TDS) and pH level also provides valuable insights into your water's overall quality and can indicate other potential issues, such as corrosion of plumbing or the presence of other minerals that might affect taste or cause health concerns over time.

Preventing Health Risks

Regular testing is your best defense against waterborne illnesses. By testing your well water at least once every year for specific indicators like total coliform bacteria, nitrates, total dissolved solids, and pH level, you can catch potential problems early. If you find harmful germs or chemicals, you can take immediate action, such as switching to bottled water, contacting your health department, or installing a suitable treatment system. This proactive approach protects everyone in your household, especially vulnerable populations like infants, young children, the elderly, and those with compromised immune systems, who are more susceptible to waterborne diseases. Without this vigilance, you risk exposing your family to pathogens that can cause diarrhea, cramps, nausea, headaches, and even kidney failure, depending on the contaminant.

What Should You Test Your Well Water For Annually?

You should test your well water at least once every year for total coliform bacteria, nitrates, total dissolved solids, and pH level CDC Guidelines for Testing Well Water. These are fundamental indicators of water quality that can reveal potential contamination or other issues. Beyond these basic tests, it's crucial to contact your local health department to find out if there are other specific germs or chemicals that are a concern in your particular area, as local conditions can vary widely. Always use a state-certified laboratory to ensure accurate and reliable results.

Essential Annual Tests

The U.S. Centers for Disease Control and Prevention (CDC) recommends a minimum set of tests for private well owners. These tests serve as a baseline to monitor the general health of your water supply.

Total Coliforms

Total coliforms are a group of bacteria that are commonly found in the environment, including soil, plants, and surface water, as well as in the digestive systems of warm-blooded animals. While many types of coliforms are not harmful themselves, their presence in large numbers can indicate that harmful germs, such as certain viruses, bacteria, and parasites, might also be present in your water. This is because coliform bacteria typically enter your water in the same ways that disease-causing germs do, often through a sewage leak or other contamination pathway. Testing for total coliforms is easier than testing for every possible pathogen, making them excellent "indicator organisms" Positive Coliform Test - What you need to know. If your total coliform count is high, it's a strong signal that your water may be unsafe to drink.

Nitrates

Nitrates are chemical compounds that can enter well water from agricultural runoff, septic systems, and other sources of human and animal waste. High levels of nitrates are particularly dangerous for infants under six months old. They can interfere with the blood's ability to carry oxygen, leading to a serious condition called methemoglobinemia, or "blue baby syndrome." While nitrates can also affect adults, infants are the most vulnerable. Regular testing for nitrates helps protect the youngest members of your household from this severe health risk.

Total Dissolved Solids (TDS)

Total dissolved solids (TDS) refer to the total concentration of all inorganic and organic substances dissolved in water. These can include minerals like calcium, magnesium, and potassium, as well as salts, metals, and some organic matter. High levels of TDS can affect the taste, odor, and appearance of your water. While not always directly harmful, a sudden increase in TDS can indicate a change in your water source, potential contamination, or issues with your well's integrity. It can also impact the effectiveness of water treatment systems, such as water softeners.

pH Level

The pH level measures how acidic or alkaline your water is. A pH of 7 is neutral, while lower numbers indicate acidity and higher numbers indicate alkalinity. The ideal pH for drinking water is typically between 6.5 and 8.5. Water that is too acidic (low pH) can be corrosive to plumbing, leading to the leaching of metals like lead and copper into your drinking water. This can pose serious health risks. Water that is too alkaline (high pH) can cause scaling in pipes and appliances, reduce the effectiveness of chlorine disinfection, and give water a bitter taste. Monitoring pH helps ensure your water is not only safe but also non-damaging to your home's infrastructure.

Localized Concerns and Certified Labs

Beyond these annual tests, local conditions might introduce other specific contaminants. For instance, areas with industrial activity might need testing for volatile organic compounds (VOCs) or heavy metals. Regions with specific geological formations could have naturally occurring arsenic or radon. Your local health or environmental department is the best resource for understanding these localized concerns and can provide guidance on additional tests you should consider.

When you decide to test your well water, always use a state-certified laboratory. These labs follow strict protocols and use validated methods to ensure the accuracy and reliability of your test results. Using an uncertified lab or a home test kit for critical parameters might give you misleading information, putting your health at risk. After you receive your results, your local health department can also help you understand what the numbers mean and recommend the next steps if any issues are found. This could involve further testing, treatment options, or advice on alternative safe water sources.

What Do Positive Coliform Test Results Mean?

A positive total coliform test result means that coliform bacteria are present in your well water. Coliforms are a family of bacteria that occur naturally in soil and decaying vegetation, as well as in the intestines of warm-blooded animals, including humans Positive Coliform Test - What you need to know. While many coliforms are harmless, their presence suggests that disease-causing microorganisms could also be in your water, or that a pathway exists for them to enter. Therefore, a positive test should be taken seriously, especially if there are vulnerable individuals in the household.

Understanding Coliforms as Indicators

Coliform bacteria are often called "indicator organisms" because their presence indicates a potential problem rather than being a direct threat themselves, in most cases. They are much easier and less expensive to test for than the wide array of specific disease-causing pathogens. If coliforms are found, it signals that your water system may be compromised, allowing other, more dangerous bacteria, viruses, or protozoan cysts to enter. "First of all, don’t panic! Yes, a positive total coliform test can mean your water is contaminated with e-coli, but not always," advises Home Water Purifiers and Filters Positive Coliform Test - What you need to know. This means a positive test is a warning sign to investigate further.

The Spectrum of Coliforms: Harmless vs. Harmful

The coliform group is broad, encompassing many kinds of bacteria. Some, like non-fecal coliforms, live in soil and decaying plant matter and are generally harmless. Their presence might indicate surface water intrusion or a problem with your well’s seal. However, the group also includes fecal coliform bacteria, which originate in the intestines of warm-blooded animals. The most well-known species of fecal coliform bacteria is Escherichia coli (E. coli).

When fecal coliforms or E. coli are detected, it's a definitive sign that your water has come into contact with human or animal waste. This is a much more serious concern because waste can contain a variety of harmful germs that can cause illness. "If E. coli or other fecal coliform bacteria are in well water, the water has come into contact with human or animal waste and could cause illness," state Joel Pigg, John W. Smith, and Diane E. Boellstorff in 'What to do About Coliform Bacteria in Well Water' What to do About Coliform Bacteria in Well Water.

Health Risks Associated with Fecal Coliforms

While many coliforms are harmless, fecal coliforms like E. coli can cause people to become sick. Symptoms of illness from these bacteria can include diarrhea, cramps, nausea, and headaches. In severe cases, especially with certain strains of E. coli such as E. coli O157:H7, the illness can lead to kidney failure, which can be life-threatening. The severity of symptoms can vary depending on the specific pathogen, the amount consumed, and the individual's immune system.

Given these potential health risks, a positive coliform test, particularly for fecal coliforms or E. coli, must be taken seriously. This is especially true if there are vulnerable individuals living in or frequently visiting the household. Infants, young children, the elderly, and people with compromised immune systems are at a much higher risk of developing severe illness from contaminated water. For these groups, even a low level of contamination can pose a significant threat. If such a test comes back positive, it's crucial to immediately switch to an alternative safe water source, such as bottled water, and consult with your local health department. They can help you interpret the results and guide you on the necessary steps to make your well water safe again. These steps might include retesting, disinfecting the well, or exploring long-term treatment solutions.

How Do You Confirm Coliform Contamination?

If your initial well water test shows a positive result for total coliform bacteria, the next step is to retest to confirm the contamination. Specifically, you should collect another water sample and have it tested for fecal coliform bacteria or E. coli What to do About Coliform Bacteria in Well Water. This retesting helps to differentiate between harmless environmental coliforms and those that signal contamination from human or animal waste. The initial positive result might sometimes be due to contamination during the sample collection process itself, which is why a confirmatory test is so important.

The Importance of Retesting

A positive total coliform test acts as an alert, not necessarily a definitive diagnosis of dangerous contamination. Coliform bacteria are very common in the environment, found in soil, plants, and even on your hands. It is possible for these bacteria to enter your water sample during collection, leading to a false positive. This is why experts like Joel Pigg, John W. Smith, and Diane E. Boellstorff recommend a retest in their guide, 'What to do About Coliform Bacteria in Well Water' What to do About Coliform Bacteria in Well Water. Retesting helps confirm if the contamination is truly from the well water itself or if it was an artifact of the sampling procedure.

Focusing on Fecal Coliforms and E. coli

While total coliforms can indicate that something is wrong, the presence of fecal coliforms or E. coli in water definitely indicates contamination by contact with human or animal waste. These specific bacteria are direct indicators of sewage or animal manure contamination, which carries a much higher risk of disease-causing pathogens. Therefore, when retesting, it is crucial to request tests specifically for fecal coliforms or E. coli. A positive result for these specific indicators means that your water has come into contact with feces, and thus, potentially dangerous germs.

Accurate Sample Collection for Retesting

To ensure the accuracy of your retest, careful sample collection is paramount. Follow the laboratory's instructions precisely, as any deviation can lead to inaccurate results. Here are key steps to take:

Preparing the Faucet

Before collecting the water sample, remove any aerator, filter, or hose from the faucet you plan to use. These attachments can harbor bacteria and contaminate your sample, leading to a false positive. Choose a faucet that is regularly used and preferably one that is not near a drain or other potential source of contamination.

Flushing the Line

Allow the water to run for several minutes (typically 2-5 minutes) before collecting the sample. This flushes out any stagnant water in the pipes and ensures you are collecting a sample representative of the water coming directly from your well.

Handling the Sample Container

The laboratory will provide a sterile sample container. Do not rinse the container or touch the inside of the container or its lid. Your hands can introduce bacteria, compromising the sterility of the sample. Wash your hands thoroughly with soap and water before handling the bottle to minimize any external contamination. Fill the container to the indicated line, ensuring it is not overfilled or underfilled, and secure the lid tightly.

Timely Delivery to the Lab

Once collected, the water sample needs to be delivered to the state-certified laboratory as quickly as possible, usually within 24 hours, and often kept refrigerated during transport. Delays can allow bacteria to multiply or die off, altering the test results and making them unreliable. Adhering to these strict collection guidelines will provide the most accurate assessment of your well water's safety. If the retest for fecal coliforms or E. coli is positive, you will need to take immediate action, such as boiling your water, using bottled water, and consulting with your local health department for treatment options.

What Are the Differences Between Coliform Types?

The differences between coliform types are important for understanding what a positive test result truly means for your well water. Total coliforms represent a large group of many kinds of bacteria, which includes both fecal and non-fecal coliform bacteria What to do About Coliform Bacteria in Well Water. Fecal coliforms, such as E. coli, are a specific subset of total coliforms that originate in the intestines of warm-blooded animals, directly indicating contamination from human or animal waste. While many coliforms are generally harmless, the presence of fecal coliforms or specific types of E. coli can pose serious health risks.

Total Coliforms: The Broad Indicator

Total coliforms are a diverse group of bacteria found widely in the environment. They live in soil, on plants, and in surface water like lakes or rivers CDC Guidelines for Testing Well Water. These bacteria generally do not make you sick. However, their presence in drinking water indicates that a pathway exists for contamination. If total coliforms are present, it means that your well water system may not be adequately protected from outside influences, and it's possible that harmful germs could also enter through the same pathway. A high total coliform count suggests that harmful germs—including certain viruses, bacteria, and parasites—are likely also in your water. This is why testing for total coliforms is recommended annually as a first-line indicator of water quality.

Fecal Coliforms: A More Specific Threat

Fecal coliforms are a specific kind of total coliform. These bacteria are found in the digestive systems (guts) of people and warm-blooded animals, and their poop (feces) contains millions of these bacteria CDC Guidelines for Testing Well Water. The presence of fecal coliforms in well water is a much more serious concern than total coliforms alone. It means the water has come into contact with human or animal waste. This direct link to fecal matter indicates a high probability that disease-causing pathogens, such as Cryptosporidium, Norovirus, Campylobacter, and Salmonella, could also be present Positive Coliform Test - What you need to know. While fecal coliforms themselves are usually harmless, their role as indicators of fecal contamination makes them a critical warning sign for potential illness.

E. coli: The Most Concerning Fecal Coliform

Escherichia coli (E. coli) is a specific species of bacteria within the fecal coliform group. It is a common inhabitant of the intestines of humans and animals. A positive test for E. coli in well water is the most definitive indicator of recent fecal contamination. This means that poop, and the harmful germs in poop, have gotten into your well water. While most E. coli strains are harmless and live naturally in our gut, some specific types of E. coli can make you seriously sick CDC Guidelines for Testing Well Water. These dangerous strains can cause severe diarrhea, abdominal cramps, nausea, and vomiting, and can even lead to kidney failure.

It is important to understand that a standard water quality indicator test for E. coli will not show whether the water contains these dangerous types of E. coli. If you suspect your water is contaminated with a dangerous type of E. coli, you would need to use a more specific type of test to find it. However, any presence of E. coli is a call to action, demanding immediate attention and remediation of the well water supply. This is why, if your initial total coliform test is positive, retesting specifically for fecal coliforms or E. coli is crucial to understand the true level of risk. The distinction helps well owners and health officials determine the urgency and type of intervention needed to ensure safe drinking water.

What Steps Should You Take After a Positive Test?

After receiving a positive test result that shows harmful germs or chemicals in your well water, the immediate and most crucial step is to stop drinking the contaminated water. Consider drinking bottled water or another safe source of water until the issue is resolved CDC Guidelines for Testing Well Water. Next, contact your local health or environmental department. They are equipped to help you understand the test results, identify the source of contamination, and guide you through the necessary steps to make your well water safe to drink again. They may also recommend that you test your well water more often in the future.

Immediate Actions for Your Safety

Your health is the top priority. If your well water tests positive for harmful contaminants, especially fecal coliforms or E. coli, assume the water is unsafe.

Secure a Safe Water Source

The first step is to immediately switch to an alternative safe drinking water source. This means using bottled water for all consumption purposes, including drinking, cooking, making ice, and preparing baby formula. You might also need to use bottled water for brushing teeth and washing dishes, depending on the severity of the contamination and the advice from your health department. Boiling your water is another option if bottled water is not readily available, as boiling kills most bacteria and viruses.

Contact Local Authorities

Your local health department or environmental department is your primary resource for guidance. They can provide expert advice based on local knowledge and regulations. They will help you interpret the specific contaminants found, their potential health risks, and the possible sources of contamination. These officials can also advise on proper well disinfection procedures, retesting schedules, and long-term treatment strategies. They may recommend testing your well water more frequently than the annual guideline, especially after a contamination event, to ensure the effectiveness of any remediation efforts.

Addressing the Source of Contamination

Understanding the source of contamination is critical for long-term solutions. Contaminants can enter your well through various pathways:

Well Integrity Issues

Cracks in the well casing, a damaged well cap, or loose seals can allow surface water, soil bacteria, or even small animals to enter the well. A professional well inspector can assess the structural integrity of your well and recommend necessary repairs.

Septic System Problems

If your home has a septic system, a failing or improperly maintained system can leak effluent into the groundwater, contaminating nearby wells. Regular septic system inspections and pump-outs are essential to prevent this. Ensure your septic system is located an adequate distance from your well, typically at least 50-100 feet, based on local codes.

Agricultural Runoff

For wells located near farms, agricultural runoff containing fertilizers, pesticides, and animal waste can seep into the groundwater. This can introduce nitrates, coliform bacteria, and other chemicals. Proper land management practices and buffer zones around your well can help mitigate this risk.

Flooding and Heavy Rainfall

Severe weather events like floods or heavy rainfall can overwhelm septic systems, cause runoff, and introduce surface contaminants directly into wells, especially if the wellhead is not properly sealed or extends above the flood plain. After such events, it is always wise to retest your well water.

Long-Term Treatment Options

Once the source of contamination is identified and addressed, you may need to implement a long-term water treatment solution. The type of treatment depends on the specific contaminants found.

Disinfection

For bacterial contamination, disinfection of the well is often the first step. This typically involves "shock chlorination," where a strong chlorine solution is introduced into the well and plumbing system to kill bacteria. After disinfection, the well must be thoroughly flushed, and the water retested to confirm the bacteria have been eliminated.

Filtration Systems

Various filtration systems can address different contaminants. For sediment and particulate matter, a sediment filter is effective. For chemical contaminants like nitrates or certain heavy metals, more advanced systems such as reverse osmosis (RO) or ion exchange might be needed. Activated carbon filters are good for removing chlorine, organic compounds, and improving taste and odor.

Water Softeners

While not directly related to bacterial contamination, hard water is a common issue for well owners. Hard water contains high levels of minerals like calcium and magnesium, which can lead to scale buildup in pipes and appliances, reduce soap effectiveness, and leave spots on dishes. Culligan offers water treatment systems for well water, including water softeners, which can help transform hard water into cleaner, soft water. These systems can provide spot-free dishes, brighter laundry, and smoother hair and skin, while also extending the life of your appliances Culligan Well Water Treatment Systems. Choosing a reliable system like those offered by Culligan ensures effective treatment for various well water challenges. When we compare different well water solutions, water softeners are a popular choice for improving water quality in homes with hard water Culligan Well Water Softeners.

Working with your local health department and a certified water treatment specialist can help you select the most appropriate and effective treatment system for your specific well water needs. Regular maintenance of any installed treatment system is also crucial to ensure its continued effectiveness and the ongoing safety of your drinking water.

Frequently Asked Questions

How often should I test my well water?

You should test your well water at least once every year. This annual testing should include checks for total coliform bacteria, nitrates, total dissolved solids, and pH level CDC Guidelines for Testing Well Water. Your local health department might recommend more frequent testing or additional parameters based on specific concerns in your area, especially after events like floods or well repairs.

What is the difference between total coliforms and E. coli?

Total coliforms are a broad group of bacteria found in soil, plants, and animal intestines. Their presence indicates a potential pathway for contamination. E. coli is a specific type of fecal coliform bacteria that originates in the intestines of warm-blooded animals, including humans CDC Guidelines for Testing Well Water. A positive test for E. coli definitively indicates contamination by human or animal waste.

Are coliform bacteria always harmful?

No, many coliform bacteria are completely harmless and are found naturally in the environment. However, fecal coliforms, like E. coli, can make people sick with symptoms such as diarrhea, cramps, nausea, and headaches Positive Coliform Test - What you need to know. The presence of any coliforms should be taken seriously as an indicator that disease-causing microorganisms might also be present.

What should I do if my well water tests positive for coliforms?

If your well water tests positive for total coliforms, the first step is to retest specifically for fecal coliforms or E. coli to confirm contamination What to do About Coliform Bacteria in Well Water. While waiting for results, consider drinking bottled water. If fecal coliforms or E. coli are confirmed, immediately switch to bottled water and contact your local health or environmental department for guidance on disinfection and further steps.

Where can I get my well water tested?

You should use a state-certified laboratory to test your well water CDC Guidelines for Testing Well Water. Your local health or environmental department can help you find a certified lab in your area and guide you on what specific tests are most relevant based on your location and any local concerns. They can also help you understand the test results.