Abstract
In the US, 23 million households rely on private wells for their drinking water, yet these wells are unregulated and unmonitored, and thus vulnerable to contamination. These exposures may lead to significant health consequences, including both acute manifestations and chronic disease. Primary care physicians often serve as the first point of contact for screening for environmental exposures and for patients with concerns about water safety. This article equips family physicians with practical guidance on the reasons and methods of testing private wells for microbiologic and chemical contaminants such as “bacteria, nitrates, arsenic, and lead”. Patient testing and relevant matrices are also reviewed. Recommendations are provided for when and how to test, interpretation of laboratory results, and how to counsel patients on mitigation strategies. Focus is placed on rural and disadvantaged communities commonly affected by contaminated well water. By integrating well water safety into routine preventive care, clinicians can play a crucial role in protecting patients from waterborne illnesses and exposures.
- Drinking Water
- Environmental Exposure
- Family Medicine
- Health Disparities
- Health Promotion
- Patient Safety
- Public Health
- Rural Health
- Water Pollutants
- Water Supply
- Waterborne Diseases
Introduction
The Clinical Importance of Private Well Water
The American Environmental Protection Agency (EPA) estimates that more than 23 million households rely on private wells for drinking water in the US.1,2 In the United States, private wells are not regulated under the federal Safe Drinking Water Act, which governs 87 potential contaminants found in public water systems.3 Instead, they are considered private drinking water sources and are the responsibility of the homeowner to test and maintain their own water supply. This translates to 15% of the US population, or 44 million people, relying on private wells that are not publicly overseen or managed.4
Some states require well construction permits or inspections, but routine testing is typically voluntary. Statewide mandates for regular private well testing are rare, with the top 5 states with the most private well protection including Maine, Iowa, Kentucky, Rhode Island, and Minnesota.5 Some states such as New Jersey, Connecticut and Florida have laws requiring well water testing during property transactions or for rental, although these requirements typically pertain to specific events rather than ongoing testing.5 In addition, in certain states such as Wisconsin, homeowners are required to disclose any known well contamination when selling their property, which may discourage some from ever testing their wells in the first place.3
In the absence of nation-wide mandatory regulations, agencies like the Centers for Disease Control and Prevention (CDC) and the EPA recommend that private well owners test their water annually for contaminants such as coliform bacteria, nitrates, and other local concerns, and conduct additional testing if there are changes in water taste, color, or odor, or after events like flooding or land disturbances.1,6 However, common water contaminants such as arsenic, nitrates and bacteria are colorless, odorless, and tasteless and can easily go undetected.3
Despite longstanding recommendations for regular testing of private wells, testing rates remain consistently low across the United States. Swistock et al. reported that 30% of well owners in Pennsylvania had never tested their wells and most had only tested once, with Jegen finding that 21% of Minnesota well owners had reported never testing.7,8 Malecki et al. reported that only 10% of well owners in Wisconsin tested their wells in the prior year.9 Stillo et al. highlighted similar findings in North Carolina and other states, identifying cost, lack of knowledge, and reliance on water taste or odor as key barriers.10 Flanagan et al. also documented significant socioeconomic disparities in testing behavior in Maine and New Jersey, with lower-income and less-educated households less likely to test for arsenic.11,12 In New Hampshire and Vermont, only 29% of private well owners tested even when free kits were distributed by clinicians.13
The goal of this article is to equip family physicians with practical, evidence-based guidance for effective patient counseling on private well water testing and remediation. By offering this resource on risk reduction strategies, our guidance aims to improve the detection and prevention of waterborne exposures especially in rural and underserved populations reliant on private wells for drinking water. Although the US Preventive Services Task Force (USPSTF) has not evaluated private well water testing as a clinical preventive service, likely due to variability in well use and regional contaminant risks, observational studies suggest that physicians, particularly in rural areas, are trusted sources for preventative health guidance. Family physicians can play a critical role by routinely asking about water sources during visits and offering region-specific testing recommendations.
The Case for Testing: Scope and Risk
A US Geologic Survey study of a sample of 2,100 private wells found that water from more than 1 in 5 wells (23%) contained 1 or more contaminants at a concentration greater than current benchmarks for drinking water, and that man-made organic compounds such as pesticides were detected in more than half (60%) of the sampled wells.4 It is well known that the availability of safe water is of paramount importance to public health, whether it is used for drinking, domestic use, food production, or recreational purposes.14 A reliable safe water supply is therefore considered a basic human right as recognized by the United Nations General Assembly in 2010.15 Access to clean drinking water is a fundamental determinant of health, and family physicians are well positioned to detect and mitigate environmental exposures related to unsafe private wells.
The American Safe Drinking Water Act describes a contaminant as any physical, chemical, biological, or radiologic element or material present in water.16 Importantly, the mere presence of a contaminant does not automatically imply a health risk. The potential threat to human health depends on the contaminant’s toxicity and the amount present in drinking water.4
Groundwater contamination can occur from sources such as septic systems, landfills, agricultural runoff, petroleum leaks, naturally occurring chemicals such as arsenic and lead, and animal waste.17 Common well water contaminants can be subdivided into 2 groups encompassing microbiologic (such as bacteria and viruses), and chemical (such as nitrates and nitrites, arsenic, radon, manganese, and lead) causes.2 When multiple chemical pollutants are found in drinking water simultaneously, their effects on health may be additive, or even synergistic.2,18
Contaminants in private wells often reflect regional environmental and industrial factors. Local public health departments can guide clinicians by highlighting area-specific risks, such as nitrates in agricultural zones, coliforms near dairy farms, radon and heavy metals in mountainous areas, or arsenic and uranium in states like Minnesota and Texas. Understanding these local concerns helps family physicians prioritize testing and provide targeted counseling. Clinicians should maintain communication with local public health for up-to-date, region-specific guidance.
Contamination risk also varies by the type of individual well being used. Shallow wells under 50 feet in depth, including dug or sand-point wells, are more prone to microbial contamination from adjacent runoff and septic systems. Deep drilled wells from 100 to 300 feet in depth access aquifers and may contain naturally-occurring contaminants such as arsenic or radium. Well casing integrity also matters as proper sealing reduces contamination risk. Lastly, contaminants such as lead may be introduced by household plumbing rather than the aquifer itself. Contamination risk varies widely, as each well and household is unique.
Health Effects of Well Water Contaminants
Private well water can harbor biological and chemical contaminants with significant health impacts:
Gastrointestinal illnesses arise from microorganisms introduced by surface runoff, underground infiltration, leaking storage tanks, or septic systems.19 Common pathogens—including Legionella, Norovirus, E. coli, Cryptosporidium, and Giardia—cause symptoms such as diarrhea, vomiting, and abdominal cramping, and can be life-threatening for young children, the elderly, and immunocompromised individuals.20 In North Carolina, private well contamination was linked to 29,400 annual emergency department visits for acute gastrointestinal illness.21
Methemoglobinemia occurs when ingested nitrate is converted to nitrite, impairing the blood’s ability to carry oxygen. The EPA established maximum contaminant levels for nitrate and nitrite primarily to protect infants from this risk, although nitrate exposure has also been associated with colorectal cancer, thyroid disease, and neural tube defects.2
Cancer and neurological effects arise from long-term exposure to arsenic, radon, and manganese. Arsenic exists in two main forms: inorganic and organic. Inorganic arsenic is toxic and linked to health problems such as cancer, while organic arsenic, commonly found in seafood, is much less harmful.22 Biological testing can differentiate between these forms to better assess exposure risk.23 Chronic arsenic exposure is linked to skin, lung, kidney, and bladder cancers, and low-level exposure in children can cause neurodevelopmental deficits.24–26 Radon, the second leading cause of lung cancer after smoking,27 is released from contaminated water during activities like showering and dishwashing and can also affect internal organs when ingested.2 Excess manganese can produce Parkinson-like neurological changes and has been associated with cognitive and attention deficits in children, as well as with cardiovascular and liver toxicity.28
Lead toxicity damages the nervous system by disrupting cholinergic, dopaminergic, and GABAergic pathways, lowering IQ and impairing cognition and behavior.24,29 Compared to children relying on community water, those using private wells have an 11% higher blood lead level, a 21% increased risk of any juvenile conduct problems, and a 38% higher risk of serious juvenile conduct problems after age 14.30
These findings underscore the urgent need for routine testing and mitigation of private well water to prevent serious, long-term health consequences, especially among children and vulnerable populations.
Clinical Guidance: When and How to Test
Testing the Well
The CDC and EPA recommend that private well owners test their water at least once a year for bacteria, nitrates, pH, dissolved solids, and other contaminants of local concern (such as arsenic or radon).1,19 Additional testing is recommended when someone in the home becomes pregnant, if a child starts living in the home, when there is a change in taste, odor, or appearance of water, after any repairs or replacements in the well system, after flooding or other environmental changes, or if there are known problems with well water in the area (Table 1). Depending on the area and its known risks, additional testing might include levels of lead, pesticides, heavy metals, or volatile organic compounds.
Recommended Water Testing for Common Chemical Contaminants
Well owners should use a certified laboratory for accurate testing since home test kits may be inaccurate and are not standardized. Local or state health departments can be contacted for a list of certified laboratories to do so. As commercial laboratory testing for private well water contaminants can range from twenty dollars in cost for basic bacterial panels to several hundred dollars for comprehensive analyses, these costs may pose barriers for some families. To address this, many states have established free or subsidized well water testing programs as summarized in Table 2. Family physicians should familiarize themselves with available local resources to support patients' access to testing. Leveraging these programs enhances the feasibility of routine well water screening as part of preventive care guidance in primary care settings.
Free or Subsidized Well Water Testing Programs by State
The EPA sets Maximum Contaminant Levels for regulated contaminants which serve as guidelines for private well owners to ensure their water is safe. Specific details are found at https://www.epa.gov/ground-water-and-drinking-water/national-primary-drinking-water-regulations. For bacteria such as coliforms and E. coli, laboratories typically use culture-based methods that involve filtering the water and incubating it to see if bacteria grow. For chemicals such as arsenic, nitrate, lead, or manganese, mass spectrometry or ion chromatography are used.
Patients usually begin well water testing by ordering a sampling kit from a certified laboratory or health department. They collect a water sample—often the first water from the tap in the morning—and send it back using a prepaid mailer or by dropping it off at the laboratory itself. Mailing is allowed for nonhazardous water samples under standard postal rules, although samples for bacterial testing must be analyzed quickly (often within 30 hours), so in-person drop-off is sometimes needed. Chemical contaminant samples are more stable and can usually be mailed without special handling.
Results are typically provided directly to the patient (sample report in Appendix I). Physicians are not automatically notified; patients may share results, however. Abnormal results are not usually reported to health authorities unless testing is part of a public health program. Families are not required to stop using their wells due to abnormal levels, but if dangerous levels of contaminants are found, they are strongly advised to use bottled water or to install treatment systems until the issue is resolved.
Clinical Assessment of Exposure
In humans, blood and urine are the preferred biological matrices for assessing exposure to heavy metals, while stool testing is used for bacterial, viral, and parasitic exposures. Hair testing is discouraged due to the potential for external contamination (such as with hair dye). While not routinely done in asymptomatic individuals, if high contaminant levels are found in a water source, or the patient is symptomatic, it is recommended to consider testing the patient.
The decision to use blood or urine depends on the chemical properties and metabolism of the specific metal, the timing of specimen collection relative to exposure, and the availability of validated testing methods (Table 3). In general, blood is preferred for evaluating acute exposures occurring within hours, whereas urine is better suited for assessing subacute (days) or chronic (weeks) exposures, as many metal compounds are rapidly redistributed and eliminated via the kidneys. For metals with long biological half-lives such as lead and methylmercury, blood is the matrix of choice due to its lower variability and more accurate reflection of total body burden compared with urine.31
Biological Testing for Well Water Contaminants in Symptomatic/At Risk Patients
Interpreting Results and Counseling Patients
Discussing water remediation options involves short-term and long-term solutions. Short-term solutions include reverse osmosis filters which remove many inorganic contaminants (such as arsenic, nitrates and lead) and are effective for potable water. These can be placed at the site of the well, at the faucet or as a free-standing water filter jug. Bottled water is a safe alternative for immediate use while long-term solutions are pursued. This is helpful for drinking, cooking, and brushing teeth. While boiling water will temper risks from coliform bacteria, if it contains nitrate or arsenic, it may increase these contaminants' concentration.
Long-term solutions involve well rehabilitation This involves cleaning the well to remove biofilm, mineral deposits and debris using mechanical or chemical methods, and sealing and grouting it to ensure the well casing is intact to prevent surface water or contaminants from entering. After disinfecting, retesting of water is paramount. If needed, well relocation may be necessary if the well is too close to a contamination source such as a septic system or agricultural runoff, or if it cannot be effectively sealed.
Well treatment systems include water softeners, anion exchange units, aeration systems and ultraviolet disinfection. Encourage consultation with a water treatment professional for specific recommendations based on the local conditions and the specific well.
Addressing Disparities in Well Water Safety
Evidence from across the United States confirms that private well water quality is shaped by both geographic and demographic factors. Studies in California,32 North Carolina,33,34 Minnesota,35 and other nationwide assessments highlight significant variability in bacterial and chemical contamination due to differences in well construction, depth, local geology, and aquifer characteristics. Fluctuating contamination over time further underscores the importance of regular, long-term testing.36
Ethnic and socioeconomic disparities in exposure and mitigation are well documented. Communities of color, including Hispanic, Black, and Indigenous populations, experience higher rates of arsenic, nitrate, and other contaminants, and are disproportionately impacted by associated adverse health outcomes, such as preterm birth.10,34,37–39 Low-income and less-educated households are also less likely to test or treat their well water, despite being at comparable risk for contamination.40 Even when free testing is available, participation is higher among more affluent and better-educated populations,41 indicating a need for interventions tailored to reach underserved and vulnerable communities.
Potential barriers to ensuring safe private well water include cost, limited awareness, linguistic challenges, and mistrust of institutions. Family physicians can help bridge these gaps by initiating water safety discussions during preventive and prenatal care visits by offering culturally sensitive counseling and connecting patients with local programs that provide free or low-cost water testing. Private well water safety is a tangible and underutilized opportunity for upstream intervention, particularly in high-risk communities. These insights highlight the urgent need for targeted, culturally responsive public health policies and clinical strategies aimed at reducing racial, ethnic, and socioeconomic disparities in well water safety and protecting vulnerable populations from preventable environmental exposures.
Conclusion
Integrating Water Safety into Primary Care
Family physicians have a pivotal role in safeguarding the health of approximately 23 million US households that rely on private wells. By incorporating water quality screening into routine care, educating patients about well contamination and mitigation, and connecting them with trusted resources such as the CDC and EPA, family physicians can reduce the risk of waterborne illnesses and serious long-term health impacts.
Practical integration of environmental health into clinical workflows can begin with simple but impactful steps (Appendix II). Intake forms should routinely ask about the source of household drinking water, enabling clinicians to identify patients at potential risk. Staff training on symptoms of waterborne illness, heavy metal exposure, and other environmental hazards can improve case detection and promote timely interventions. Clinicians may also collaborate with local laboratories or environmental health agencies to facilitate low-cost or grant-funded water testing for at-risk patients, particularly those in underserved or high-exposure areas (Table 4).
Common Well Water Contaminants: Mitigation Options and Estimated Costs
Beyond the clinic, family physicians can extend their influence through community education. Hosting seasonal workshops on well maintenance, testing intervals, and treatment options creates accessible entry points for public engagement. Patient-facing materials should be easy to understand, visually clear, and tailored to common regional risks such as nitrates in agricultural zones or arsenic in certain geologic areas. Collaboration with local public health departments enhances the reach of clinical efforts. Physicians can help promote free or subsidized testing initiatives, refer families to environmental health officers for well inspection and remediation guidance, and advocate for broader state-level investments in rural water infrastructure and safety programs. Creating referral networks of trusted contractors and treatment system providers also facilitates access to mitigation resources. These initiatives not only safeguard patient health but also reinforce the family physician’s role as a trusted advocate for environmental justice and rural public health leadership.
Resources for Patients and Clinicians
CDC Private Wells website: https://www.cdc.gov/drinking-water/safety.
The U.S. Environmental Protection Agency (EPA) Safe Drinking Water Hotline at (800) 426-4791 and website: https://www.epa.gov/privatewells.
Respective state and local public health departments.
Acknowledgments
ChatGPT was used for truncating the manuscript to lower word count from the original manuscript. ChatGPT with GPT-4o was used, version released by OpenAI in May 2024.
Appendix
Appendix I - Private Well Water Testing Report Sample
Client ID: Anonymous
Location: Rural Midwest, USA
Date Collected: 2025-07-22
Date Reported: 2025-07-30
BACTERIA
METALS
NITRATES & NITRITES
OTHER PARAMETERS
Summary of Findings:
Arsenic is slightly above the EPA maximum contaminant level.
Iron and manganese are elevated, causing potential taste/staining issues but not immediate health concerns.
Water is moderately hard and slightly acidic, which may affect plumbing.
No bacterial contamination detected.
Recommendations:
Install point-of-use arsenic filter (reverse osmosis or adsorptive media).
Consider water softener for hardness and pH correction system.
Retest arsenic annually and test for bacteria every 12 months.
Appendix II - Practical Tools to Promote Private Well Water Safety in Patients
Clinical Integration
Add water source screening to new patient and annual visit intake forms.
Train staff to recognize symptoms of waterborne illness or heavy metal exposure.
Partner with local laboratories or public health programs to offer free or low-cost well testing.
Patient Outreach
Host seasonal community workshops on well testing, maintenance, and treatment options (with the appropriate professionals).
Distribute plain-language, culturally appropriate flyers on common local contaminants (e.g., nitrates, arsenic, lead).
Offer contaminant-specific filtration guidance rather than generic filter recommendations.
Collaboration & Advocacy
Collaborate with county and state health departments to promote subsidized testing programs.
Refer families to environmental health officers for well inspections or remediation support. See Table 4 for free or low-cost programs.
Advocate for state-level funding for rural water safety infrastructure and testing access.
Support for Patients
Build a referral list of vetted well repair contractors and water system specialists.
Offer telehealth follow-up for patients with potential exposure to contaminants.
Use grant opportunities to install point-of-use water filtration systems in clinics serving at-risk populations.
Notes
This article was externally peer reviewed.
Funding: Support from the Department of Family Medicine, Mayo Clinic, was provided in the form of dedicated research time for Dr. Jegen. No specific funding was received.
Conflict of interest: None.
- Received for publication June 26, 2025.
- Revision received August 4, 2025.
- Accepted for publication August 25, 2025.
