Private Well Water Safety: What 43 Million Americans Need to Test For

A private well draws water from underground — either from a shallow water table (dug wells and driven wells) or from deeper aquifers (drilled wells). The water has been filtered naturally through layers of soil and rock, which removes many surface contaminants.

This natural filtration is effective for a lot of things. Most groundwater is free of the microbial contamination that makes surface water risky. It doesn't need to be disinfected with chlorine the way river or lake water does. Deep aquifers in particular tend to be stable, consistent, and naturally clean — or at least they were, before human activities introduced new contamination sources.

The problem is that over the past century, agricultural practices, industrial activity, underground storage tanks, septic systems, and waste disposal have introduced a wide range of contaminants into groundwater that simply weren't there before. Nitrates from fertilizer and septic systems. Arsenic from natural deposits disturbed by development. Agricultural chemicals. Industrial solvents. PFAS from firefighting foam. Radon from natural radioactive deposits.

The contaminants present in any specific well depend heavily on local geology, land use history, and how the well was constructed and maintained. There's no universal answer to "is my well water safe" — it depends on testing your specific well.

Unlike public water systems, private wells don't get tested by default. Testing only happens when the owner initiates it. Many well owners test when they first move in and never test again — which is a significant gap given that groundwater quality can change over time as new contamination sources develop.

Environmental and public health professionals generally recommend that private well owners conduct a baseline test when they first start using a well, after any event that could affect water quality (flooding, new nearby construction, changes in water taste or appearance), and at minimum once a year for the basic parameters.

Total coliform bacteria. This is the non-negotiable first test. Coliform bacteria are indicator organisms — their presence in water suggests that the well may have been contaminated by surface water, animal waste, or septic system leakage, and that disease-causing organisms may be present. E. coli (a specific type of coliform) indicates direct fecal contamination and is particularly dangerous. Total coliform testing is inexpensive (typically $20 to $50) and should be done annually at minimum.

Nitrates. Nitrate contamination in private wells is extremely common in agricultural areas and in areas with high density of septic systems. The EPA limit for public water systems is 10 mg/L as nitrogen, and that's a reasonable threshold for private wells too. Nitrate above this level is dangerous for infants under 6 months. Nitrate testing costs around $15 to $30.

pH. The pH of your water affects both its safety and its effects on your plumbing. Very acidic water (low pH) can leach lead and copper from pipes. Very alkaline water can cause scale buildup. The ideal range for drinking water is 6.5 to 8.5. A basic pH test is inexpensive and often included in standard well testing panels.

Hardness. While not a health issue, very hard water causes scale buildup in pipes and appliances and is relevant for deciding whether to install a water softener. Often included in standard panels.

These four parameters are the baseline minimum for annual testing. Depending on where you live and local environmental conditions, you should also test for additional contaminants.

Beyond the baseline, what you test for should be informed by your specific local conditions. Here's a guide to additional tests worth considering.

Arsenic. Naturally occurring arsenic is present in bedrock and soil across many parts of the United States — New England, the upper Midwest, the Mountain West, and parts of the South. If you're in one of these regions or if your neighbor has detected arsenic, test for it. Arsenic is colorless, odorless, and tasteless, and long-term exposure above the EPA limit (10 ppb) increases cancer risk. Arsenic testing typically costs $20 to $40.

Lead. Unlike in public water systems, lead in well water usually doesn't come from the well itself — it comes from the plumbing inside the house. But some older well casings and pumps contain lead-bearing materials. If your home was built before 1986, test for lead. Testing costs around $20 to $40.

Radon. Radon is a naturally occurring radioactive gas produced by the decay of uranium in bedrock and soil. In groundwater, radon can be present at elevated levels — particularly in New England (especially Maine, New Hampshire, and Vermont), the mid-Atlantic states, and parts of the Southeast. When you run water from a well with high radon levels, the radon is released into the air in your home. This is primarily an inhalation concern rather than a drinking concern, but it's worth testing if you're in a high-radon region. Radon testing in water costs around $25 to $35.

PFAS. If your well is located within a few miles of a military base, airport, industrial site, landfill, or an area where biosolids were applied as fertilizer, PFAS testing is worth prioritizing. PFAS don't occur naturally — their presence indicates contamination from industrial sources. Testing for a comprehensive PFAS panel costs $150 to $400, depending on the number of compounds.

Volatile Organic Compounds (VOCs). If you live near gas stations, dry cleaners, industrial facilities, or in an area with known underground storage tank leaks, testing for VOCs — including benzene, toluene, and chlorinated solvents — is worth doing. A standard VOC panel costs $50 to $100.

Manganese and iron. These naturally occurring minerals are common in well water. They're not dangerous at typical levels but cause staining (rust stains from iron, black staining from manganese) and can affect taste significantly. If you have discolored water or staining on fixtures, test for these.

Agricultural chemicals. If you live in a farming area where pesticides and herbicides are applied, testing for relevant agricultural chemicals may be appropriate. Your local cooperative extension office or state environmental agency can advise on which chemicals are of concern in your specific area.

There are several ways to arrange for well water testing.

State-certified laboratories. The most reliable approach is to use a laboratory certified by your state for drinking water analysis. Using a certified lab ensures the testing methods meet regulatory standards and the results are legally defensible. Your state health or environmental agency maintains a list of certified labs. Many offer mail-in testing kits — you collect the sample yourself following their instructions and mail it in.

Your state or local health department. Many state and county health departments offer free or subsidized well water testing programs. In some states, this includes annual free testing for basic parameters. Contact your local health department to find out what's available in your area.

University cooperative extension programs. Land-grant universities in many states operate water testing programs, often at reduced cost compared to commercial labs. These programs frequently have particular expertise in locally relevant contaminants.

Commercial testing services. Companies like National Testing Laboratories, SimpleLab, and Tap Score offer mail-in testing with varying levels of comprehensiveness. These can be convenient and reasonably priced. Look for companies that partner with certified labs for analysis.

When collecting water samples for testing, follow the laboratory's instructions precisely. For bacterial testing in particular, collection technique matters significantly — improper collection can result in false positives or false negatives.

One important note: don't use a water treatment company to test your water. Some companies offer "free" testing but use the results — accurately or inaccurately — to sell you treatment systems. Get an independent assessment first.

Finding a contaminant in your well water is concerning, but it's solvable. Here's how to approach specific findings.

Bacterial contamination. If coliform or E. coli is detected, the immediate response is to stop drinking the water and use bottled water or boil water (rolling boil for at least 1 minute) for all drinking and cooking. Then contact a licensed well contractor to inspect the well for structural problems — cracks in the casing, improper sealing, or proximity to contamination sources. The well may need to be shock-chlorinated (a disinfection procedure using chlorine) and retested. Don't just shock-chlorinate and assume the problem is solved without addressing the underlying cause.

Nitrate contamination. If nitrates are above 10 mg/L, use bottled or filtered water (reverse osmosis removes nitrates) for infant formula and drinking while you investigate the source. If you're in an agricultural area, the contamination may be ongoing, in which case a permanent treatment system (reverse osmosis or ion exchange) is the practical solution.

Arsenic above 10 ppb. Install a point-of-use treatment system — reverse osmosis is effective for arsenic, as is activated alumina filtration for certain forms of arsenic. The specific form of arsenic in your water (arsenite vs. arsenate) affects which treatment technology works best, so getting a speciated arsenic test is helpful if levels are elevated.

PFAS detection. Reverse osmosis systems and whole-house granular activated carbon systems are the most reliable options. For drinking and cooking, a reverse osmosis system under the kitchen sink is the most practical solution.

In all cases, retest after installing any treatment system to verify it's working as expected. Treatment systems can fail, and filters need replacement — don't install a system and assume indefinitely that it's doing its job.

Well maintenance is the most underappreciated aspect of private well ownership. A well that's maintained properly is much less likely to develop contamination problems.

Have your well inspected by a licensed well contractor every five to ten years. The inspection should cover the well casing (checking for cracks and corrosion), the well cap and seal (making sure they're intact to prevent surface water intrusion), the area around the wellhead (checking for proper grading to direct water away from the well), and the pump and pressure system.

Keep potential contamination sources away from your well. The EPA recommends maintaining minimum separation distances between your well and septic system components (typically 50 feet), fuel storage tanks (50 feet), fertilizer and pesticide application areas (50 feet), and animal enclosures and waste storage (50 feet).

Don't use your well casing as a support post for anything or run electrical lines along it. Keep the area around the wellhead clear of debris and standing water.

Never pour anything down an old, unused well. Improperly abandoned wells can be a direct conduit for surface contamination to reach groundwater. If you have an unused well on your property, it should be properly decommissioned by a licensed contractor.

Test your water at least annually for bacteria and nitrates, and more comprehensively every 3 to 5 years or whenever you notice changes in water quality, taste, smell, or appearance.