Private well owners should test for total coliform bacteria, nitrates, total dissolved solids, and pH every year at minimum. Unlike public water systems, private wells have no federal monitoring requirements, so the responsibility falls entirely on you. Beyond that baseline, your location, geology, and nearby land use determine which additional tests are worth the money.
The Four Annual Tests Every Well Needs
The EPA and CDC both recommend the same core panel once a year: total coliform bacteria, nitrates, total dissolved solids (TDS), and pH. These four cover the most common and most dangerous contamination risks for private wells.
Total coliform bacteria is a screening tool, not a direct measure of disease-causing organisms. A positive result means surface water or fecal material may have entered your well, which signals that harmful pathogens could be present too. A negative result means no contamination was detected at the time of sampling.
Nitrates are particularly dangerous for infants under six months old. Levels above 10 milligrams per liter can cause a serious condition where the blood can’t carry enough oxygen. Nitrates commonly enter groundwater from fertilizer runoff, septic systems, and animal waste. One important detail: boiling water does not remove nitrates. It actually concentrates them by evaporating water while the nitrate stays behind.
Total dissolved solids measures the overall mineral content of your water. High TDS can affect taste and indicate other contamination issues. pH tells you how acidic or alkaline your water is. Water that’s too acidic can corrode pipes and leach metals into your drinking supply, which connects directly to the next category of concern.
Heavy Metals: Lead, Arsenic, and Uranium
Lead contamination in well water typically comes from corrosion of plumbing materials rather than the groundwater itself. If your home has older pipes, solder joints, or brass fixtures, a lead test is worth running at least once. The federal action level for lead is 0.010 mg/L, and there is no safe level of lead exposure for children. Testing for lead requires a specific “first draw” sample collected after water has sat in your pipes undisturbed for at least six hours, so the protocol differs from your standard bacteria test.
Arsenic and uranium are geological contaminants, meaning they occur naturally in certain rock formations. Bedrock wells in New England, the upper Midwest, and parts of the Southwest are particularly prone to elevated arsenic. The federal limit for arsenic is 0.010 mg/L. You can check with your state geological survey or health department to find out whether your area has known arsenic or uranium issues. If it does, test at least once, and again if you deepen or modify your well.
Copper, manganese, and iron are less dangerous but affect taste, staining, and plumbing. If you notice blue-green stains (copper), black stains (manganese), or rust-colored water (iron), targeted testing can confirm the source.
Pesticides and Industrial Chemicals
If your well is near agricultural land, testing for pesticides and herbicides makes sense. Common compounds detected in agricultural groundwater include atrazine (federal limit 0.003 mg/L) and other crop chemicals that can persist in soil for years. You don’t need to know the exact chemicals by name. Labs offer agricultural contaminant panels that screen for the most common ones.
Wells near urban areas, gas stations, dry cleaners, or industrial sites face a different set of risks: volatile organic compounds (VOCs). USGS research found that solvents and fuel-related chemicals show up in groundwater beneath urban areas at measurable rates. Even wells near forested land can pick up VOCs from nearby roads or upgradient agricultural activity. If you live within a mile of any current or former industrial site, a VOC panel is a reasonable precaution.
PFAS: The Newer Concern
Per- and polyfluoroalkyl substances, commonly called “forever chemicals,” now have federal drinking water limits. The two most studied compounds, PFOA and PFOS, have maximum contaminant levels of 0.000004 mg/L, which is 4 parts per trillion. That’s an extremely low threshold, reflecting how toxic these substances are even in tiny amounts. Wells near military bases, airports, firefighting training sites, or certain manufacturing facilities face the highest risk. PFAS testing is more expensive than basic panels, but if you’re in a high-risk area, it’s worth doing at least once.
When to Test Beyond the Annual Schedule
The yearly test covers your baseline. But several situations call for immediate retesting:
- Flooding or land disturbance near your well, which can push surface contaminants into groundwater
- Any repair or replacement of well components, since construction can introduce bacteria
- Changes in taste, color, or smell, which often signal new contamination
- A pregnancy or a new infant in the household, because nitrate and lead risks increase for vulnerable populations
- Notification of local water problems from your county or state health department
Spring is also a good time for a mechanical inspection of the wellhead, casing, and cap, since winter freeze-thaw cycles and snowmelt can create new entry points for contamination.
How to Collect a Valid Sample
Bad sampling technique produces bad results, and you’ll waste your money. The basics apply to most tests: choose a cold water faucet that doesn’t have a filter, aerator, or hose attached. Kitchen sinks and bathtub faucets work well. Run the water for two to three minutes until the temperature stabilizes, which clears standing water from the pipes and gives you a sample of actual groundwater.
Bacteria samples have stricter rules. You’ll use a sterile bottle (usually 125 or 150 mL) provided by the lab. Wear gloves, don’t rinse the bottle, don’t set the cap down on any surface, and don’t touch the inside of the bottle or cap. Fill to just above the 100 mL line, leaving about an inch of headspace. Cap it immediately and keep it on ice until it reaches the lab.
Lead and copper samples are the opposite of everything above. You want the water that’s been sitting in your pipes, not flushed water. Let the tap sit unused for at least six hours (overnight works), then collect the very first water out of the tap in a wide-mouth bottle without flushing first.
What Testing Costs
Individual tests through a certified lab typically run between $13 and $77 each. For reference, a coliform and E. coli bacteria test costs around $52, nitrate testing runs about $40, pH is around $13, and total dissolved solids is roughly $29. A basic annual panel covering all four recommended tests will generally land between $100 and $150.
Heavy metal tests, pesticide screens, and VOC panels cost more and are usually subcontracted by smaller labs. A comprehensive panel covering metals like lead, arsenic, copper, iron, manganese, and sodium is typically available on request. PFAS testing can run $200 to $500 or more depending on the number of compounds screened.
Your state health department or cooperative extension office can point you to certified labs in your area, and some states offer subsidized testing programs. Use only labs certified under your state’s drinking water program, since uncertified results may not be reliable and won’t be accepted if you ever need documentation for a real estate transaction or legal dispute.