Testing a well: what to order, how to take each sample, how to read the report

The short answer: every year, have a state-certified lab test your well for total coliform bacteria, nitrate, total dissolved solids and pH. Add other tests (arsenic, uranium, radon, manganese, lead, PFAS, VOCs) based on your area, your plumbing and what is near the well. Then collect each sample exactly the way that lab's instruction sheet says, because a sample taken the wrong way gives you a confident-looking number that means nothing.

Most guides stop at "use a certified lab." This one also covers where well tests actually go wrong: the sample (which tap, how long the water sat, how fast it reaches the lab) and the report (units, reporting limits, which benchmark applies). Every figure links to the official page it came from.

Why nobody else is testing your well

If your water comes from a utility, someone is legally required to test it. If it comes from your own well, that someone is you. EPA's private wells page says the quality and safety of water from private domestic wells is not regulated by the federal government under the Safe Drinking Water Act, that most state governments don't regulate it either, and that "private well owners are responsible for delivering safe drinking water to their households." EPA puts the number of people on private wells at over 43 million, about 15 percent of the U.S. population.

So the federal limits on your lab report (MCLs) were written for public water systems. They are still the usual yardstick for a well result, and we use them that way here, but nobody enforces them at your tap. EPA also says that it is unable to test residential drinking water on request; it sends well owners to their state program or to a certified lab.

A few states do require testing at specific moments. New Jersey's Private Well Testing Act, for example, requires testing of raw (untreated) well water whenever a property is sold and every five years for leased properties, according to the New Jersey Department of Health.

The baseline panel: four tests every year

The federal advice is short and consistent. CDC's guidelines for testing well water say to test at least once each year for total coliform bacteria, nitrates, total dissolved solids and pH, using a state-certified laboratory. EPA's Protect your home's water page uses the same four.

Each of the four answers a different question:

• Total coliform bacteria is an indicator. EPA's drinking water regulations table describes total coliforms as not a health threat in itself but a sign that other, potentially harmful bacteria may be present. Many labs report E. coli alongside it; Vermont's state lab sells its homeowner kit as "Coliform/E. coli." More on this in the coliform bacteria explainer.
• Nitrate is the main reason infant households test. EPA's limit for public systems is 10 mg/L measured as nitrogen. See the nitrate explainer for the health background.
• Total dissolved solids (TDS) and pH are general-condition checks. EPA's secondary (non-enforceable) standards are 500 mg/L for TDS and 6.5 to 8.5 for pH. Penn State Extension notes that water with a pH below 6.5 or above 8.5 can corrode lead and copper, which is why a low pH is a cue to test for lead at the tap.

Beyond those four, official schedules differ, largely because each state sees different problems in its groundwater:

Sources: MDH well testing, NJ DOH (above), Vermont residential testing and its radon-in-water kit sheet, Penn State Extension, NDSU WQ1341.

The yearly panel is a floor. A clean yearly result says nothing about arsenic or uranium, because they weren't in the test.

What actually turns up in wells

The largest national look at untreated domestic-well water is a USGS study that sampled wells in 30 principal aquifers between 1991 and 2004 (USGS Scientific Investigations Report 2008-5227). No single contaminant exceeded a health benchmark in more than 8 percent of wells. Taken together, though, about 23 percent of wells had at least one contaminant above a benchmark, and most of those contaminants were natural, coming from rock and soil rather than from anything the owner did.

Notice what is not in the yearly panel: arsenic, manganese, uranium and radon. Organic compounds (pesticides, solvents) were often detected at low levels but rarely above a benchmark. The same study detected total coliform bacteria in 33.5 percent and E. coli in 7.9 percent of the wells where bacteria were measured, which is why bacteria stay on the yearly list.

The yearly-panel parameters also caught a lot. In the USGS data, about 16 percent of wells had pH outside EPA's 6.5 to 8.5 range, and TDS was above 500 mg/L in about 15 percent.

Nitrate, unlike most of the list, is tied to human activity, and it shows when wells are grouped by surrounding land use:

The authors caution that their wells are not a statistically representative national sample, and the water was sampled before home treatment. Treat these as signals, not your odds.

Test for X if Y: situational tests

The table below is built only from triggers that a federal, state or extension source names. EPA's conditions table on its Protect your home's water page carries most of it; state schedules fill in the contaminants EPA's table leaves out. Each row links to our explainer and to the lab finder filtered for that test.

Flooding, land disturbance, new construction and work on the well are general reasons to test again; CDC and EPA don't tie them to one contaminant (see when to test below). EPA's table lists lead with pH and copper, and Penn State and New Jersey explain why: corrosive, low-pH water picks up metal on its way to the faucet, so a lead test tells you about your pipes as much as your aquifer. The PFAS row is deliberately narrow. EPA's PFAS and private wells page says EPA does not regulate or provide recommended standards for private wells, and it lists contaminated waste sites, manufacturing waste and firefighting foam as sources of PFAS exposure, not as triggers for a test. Your health department knows whether PFAS is a local issue. EPA's May 18, 2026 proposals to change the public-system PFAS rules are not final, and the 2024 limits stand; the PFAS explainer follows them.

Certified lab vs. home test strips

"State-certified" has a specific meaning. Under EPA's drinking water lab certification program, a certified lab must use approved methods, pass periodic on-site audits, and successfully analyze proficiency-testing samples at least once a year for each method and analyte. Certification is earned test by test. A lab certified for bacteria is not automatically certified for arsenic, and a lab certified for metals as a group may or may not run the exact compound you want.

That is how we built this site's lab finder. Every listing comes from an official state list (see sources). Where the list names the analyte for that lab, we show it as named; where the lab holds only a parent group such as "inorganics," we show it as group-level, and you should confirm the specific test by phone.

The other question is whether a lab takes samples from homeowners at all. Some certified labs only serve utilities. Only a few states publish this. On our site, Connecticut has an explicit private-well testing column, Minnesota's list contains only labs that accept private-well samples, Vermont highlights labs that accept private samples, and Washington marks labs that accept commercial or public samples (a broader label, so call first). The finder's "Accepts samples from the public" toggle uses those flags. Other states, such as New York (PFAS-rebate table only so far) and Pennsylvania (a 2024 list), don't publish a homeowner flag; the state pages explain each list's limits.

What about home test strips?

None of the federal or state pages cited here recommends a home strip or kit as the basis for a health decision; all of them point to certified labs. Penn State Extension also warns readers to be cautious of results from any uncertified lab or from water treatment salespeople.

The best evidence on kit performance is a peer-reviewed Virginia Tech study of 16 at-home lead test brands (Kriss and others, Environmental Science & Technology, 2021). Twelve of the sixteen had detection limits of 5 to 20 mg/L. That is 5,000 to 20,000 µg/L, or several hundred to more than a thousand times EPA's 15 µg/L action level for lead in public systems. The better binary strips caught dissolved lead but were only 28.6 percent accurate on water containing particulate lead alone. Strips are not a substitute for a lab: for anything you would act on, use a certified one.

How to test a well, step by step

1. Call your county or state health department first. EPA notes that your local health department may provide private well testing for free, and it will know which contaminants turn up in your area. CDC says your health department, environmental department or county government should have a list of certified labs.
2. Pick a lab and confirm four things by phone. Use the finder or your state's list, then ask: Are you currently certified for this exact test? Do you accept samples from homeowners? What do the sample kit and shipping cost? What is the time limit between collection and analysis? Minnesota's health department suggests contacting a few labs to compare costs.
3. Order the kit and read the instructions before sampling day. You may need to freeze ice packs ahead of time.
4. Choose the day. Bacteria samples are time-limited, which is why, as Penn State Extension notes, "most labs will not accept water samples on Fridays or before holidays." Sample early in the week unless your lab says otherwise.
5. Collect each sample as that test requires, and record the date, time and any treatment equipment.
6. Ship or drive it in the same day. Then keep the report. NDSU Extension recommends keeping copies of all results so you can see changes over time.

Collecting samples: each test wants something different

Every test type in one table, with the container, preservative, time limit and the reason for each step, is in how to collect a well water sample.

Instructions for different tests from the same state lab contradict each other on purpose, because each test answers a different question. Vermont's homeowner package is a good example: you leave the faucet aerator on for the lead sample and take it off for the bacteria sample.

Sources: Vermont Department of Health Laboratory Homeowner's Testing Package instructions, lead and copper homeowner instructions and radon kit sheet; NDSU WQ1341; Penn State Extension.

Bacteria: why the clock matters

Coliform tests only find bacteria still alive when the lab starts. Montana State University's Well Educated program explains the consequence: a sample that sat too long can come back "Absent" because the bacteria died in transit, so a late "Absent" result is unreliable and worth repeating. A "Present" result, on the other hand, is reliable however long it took, because bacteria cannot appear in a sealed sample. MSU notes that there are no hold-time requirements for private-well samples (the 30-hour limit is what public water supplies must meet), but results are more reliable within 30 hours, and a sample more than 48 hours old is likely not reliable. Montana's program flags late samples with an "H" qualifier (MSU Extension).

Lead: the first draw is the point

Vermont's lead instructions describe the two techniques: a "draw" sample shows how much lead dissolved into water that sat in your pipes for six hours or more, and a "flush" sample shows whether running the water clears it. A flushed sample alone can miss the water your family drinks first thing in the morning. Vermont's package says to fill the first-draw bottle before any other.

Radon: bubbles ruin it

Radon is a gas, and it escapes into any air pocket. Vermont's instructions say to turn the capped vials over and tap them; if you see air bubbles of any size, empty the vials and start again. Penn State Extension notes that in Pennsylvania some specialized tests, radon among them, usually require a lab employee to collect the sample, so ask your lab who samples before you order.

Treated or untreated water?

Sources disagree here too. NDSU says to take a "raw" sample that bypasses treatment if possible, and New Jersey's sale-time test must use raw water. Minnesota says that if you treat your water, test the water after treatment. The raw sample tells you about the well; the treated one tells you what you drink. With a softener or filter you may want both. Vermont's form asks you to describe any treatment and write "bypass treatment" if you bypassed it.

Who should take the sample

For routine tests, homeowners usually collect their own samples. Penn State Extension recommends a disinterested third party when legal action could follow, such as a dispute with a nearby drilling or industrial operation. New Jersey's sale-time testing uses labs certified for sample collection.

When to test, beyond the yearly panel

EPA and CDC add occasions outside the yearly schedule: known problems with groundwater in your area, flooding or other changes near the well, any repair to the well system, a change in odor, color or taste, and a pregnancy or a child coming to live with you. Minnesota adds a retest after any corrective action and a test of treated water if you treat, and New Jersey requires testing when a home with a well is sold (and every five years for rentals). State-by-state schedules, and one section for each of the nine events that call for an extra test (flood, wildfire, a new baby, farms or septic nearby, oil and gas drilling, a new well, repairs, a home sale, a change in the water), are in how often to test well water.

What a well test costs

Only public price lists are quoted here. Vermont's state health laboratory publishes one on its forms page (page updated October 30, 2026; read November 1, 2026):

At the other end, the New Jersey Department of Health puts the average cost of a full Private Well Testing Act panel at $1,250 (fact sheet updated January 2023). That panel covers bacteria, 29 VOCs, nitrate, lead, arsenic, synthetic organic chemicals, PFAS, iron, manganese and pH, plus mercury, gross alpha and uranium in some counties, and the samples are collected by a certified firm. Cost tracks the number of analytes and the kind of analysis. Vermont's own list shows the spread: $14 for bacteria, $120 for VOCs and $630 for its synthetic organic chemicals group.

To keep cost down, ask your health department about free testing, and order situational tests based on the table above rather than a yearly "test everything" panel, which Penn State Extension calls "very expensive and unnecessary."

Reading the report

A full column-by-column walk-through of a well water quality test report, with a decoded sample, qualifier letters, holding times and worked examples, is in how to read a well water test report. The short version: check four things on every line, the analyte, the result, the unit, and the limit the lab could measure down to.

Sources: NDSU WQ1341 (mg/L and ppm, µg/L and ppb); EPA's PFAS rule page (ppt also expressed as ng/L); Virginia Cooperative Extension Nitrate in Household Water (nitrate-N conversion).

Four traps catch most people. First, "ND" or a value such as "<0.5" means below the lab's reporting limit, not zero; Minnesota's health department, in its guide to interpreting lab results (June 2026), notes that reporting limits "can and do change," so check that the limit is well below the benchmark you care about. Second, nitrate can be reported "as N" or "as NO₃": 14 mg/L as N is above the 10 mg/L public-system limit, while 14 mg/L as NO₃ is about 3.2 mg/L as N. Third, the benchmarks differ. An MCL is enforceable only for public systems; the MCLG is the level with no known or expected health risk, and it is zero for arsenic, uranium and lead; an SMCL covers taste, odor and staining; and EPA's health advisories are not legally enforceable standards. Fourth, a "Total coliform: Present, E. coli: Absent" result still calls for action: Minnesota's advice for any coliform detection is a safe alternative source, disinfection of the well and system, and a retest.

To check a number against its benchmark, use the results checker; our contaminant explainers give each benchmark with its source.

What to do with a bad result

1. For bacteria or high nitrate, stop drinking it for now. Minnesota's guidance for coliform is to use a safe alternative source until the problem is fixed; boiling is an option only if nitrate is not detected. For nitrate above 10 mg/L, Minnesota says "Do NOT boil the water—boiling will increase the nitrate concentration," and to use an alternative source.
2. Re-test to confirm. New Jersey's health department suggests retesting to make sure the first sample was collected and analyzed properly. Use a certified lab and follow its sampling sheet exactly.
3. Call your health department. EPA says to contact your public health department for specific steps when a contaminant exceeds health standards. If an infant, a child or someone pregnant drinks the water, ask your doctor or the health department what to do in the meantime.
4. Fix the source if you can. For bacteria, Minnesota says to disinfect the well and water system; for nitrate, Minnesota suggests a licensed contractor inspect the well and that you remove nearby nitrate sources. New Jersey also lists a new or deeper well, septic repairs, or connecting to a public supply.
5. Choose treatment for the specific contaminant. For PFAS, EPA names granular activated carbon, reverse osmosis and ion exchange resins. Ask for proof that a system is independently certified to reduce your contaminant, and know that New Jersey notes there are no state regulations for water treatment professionals there; get several quotes.
6. Re-test after treatment, then on your normal schedule. Minnesota says to retest after any corrective action, and to test the treated water.

Each contaminant explainer has its own next steps: nitrate, coliform bacteria, arsenic, lead, PFAS, uranium, radon, manganese and VOCs. When you're ready to order, the lab finder lists state-certified labs by test.

This guide is general information, not medical advice. Federal limits quoted here apply to public water systems, not private wells.

Questions people ask