Well Water Testing: What to Test, When, and What It Costs

The EPA and CDC recommend a bacteria and nitrate test every year. Most private wells never get one.

The federal Safe Drinking Water Act does not cover private wells. The roughly 43 million Americans on well water get no monitoring, no treatment, and no alerts from any agency - if fertilizer runoff, a failing septic system, or naturally occurring arsenic reaches your aquifer, nobody will tell you. Testing is entirely the owner's job, and it is the only maintenance task on a well that directly protects your family's health.

One more thing before the schedule: well water testing rules and help vary sharply by state. Some states require a water test at property transfer or when a new well is drilled, and several will test your water for free (list below). The well owner guide for your state covers your local testing requirements, well codes, and health-department contacts.

The annual baseline is simple: every spring, test for total coliform bacteria, nitrates, total dissolved solids (TDS), and pH. Spring is the right time because snowmelt and heavy rain maximize surface runoff - if contaminants are going to reach your wellhead, that is when it happens. Collecting the sample and reading the results are completely DIY-safe; only structural repairs that the results uncover need a licensed well contractor.

Fourteen contaminants cover virtually every private-well problem in the U.S. Here is what each one does, the EPA limit, what the test costs, and how it is treated.

Lab reports compare your water against EPA limits: the enforceable Maximum Contaminant Level (MCL) for health threats and the non-enforceable Secondary MCL (SMCL) for nuisance issues like staining and taste. Private wells are exempt from enforcement, but these thresholds remain the gold standard for judging whether your water is safe.

Most of these contaminants have their own deep-dive guide covering health effects, testing, and treatment in detail: arsenic, lead, nitrates, coliform bacteria, PFAS, radon, uranium, iron, VOCs, and trihalomethanes. For the full picture of what can be in a private well and where it comes from, start with our well water contaminants guide.

A note on PFAS (2024-2026): in April 2024 the EPA set first-ever limits for six PFAS "forever chemicals," including an ultra-trace 4.0 parts per trillion for PFOA and PFOS - roughly one drop diluted across twenty Olympic pools. In 2026 the agency proposed extending public-system compliance deadlines to 2031 and rescinding the limits for four secondary PFAS compounds. None of that regulatory back-and-forth applies to your well, and the health science is unchanged: if your well tests above 4.0 ppt for PFOA or PFOS, install a certified granular activated carbon or reverse osmosis system.

Answer a few yes/no questions about your home and surroundings, and get a recommended test panel with a real cost estimate.

Every contaminant on the master table arrives by one of four routes - three from above, one from below.

Understanding the pathways tells you what to test for. Agricultural runoff carries nitrates and pesticides down through the soil into shallow aquifers - which is why farm-country wells test for nitrates without exception. Septic leachate from a failing or too-close drainfield delivers bacteria, viruses, and nitrates; 100 feet is the common minimum separation for good reason. Surface water rides straight down the casing when a well cap is cracked or the sanitary seal fails - the classic cause of a sudden coliform hit after heavy rain. And from below, naturally occurring arsenic, uranium, and radon dissolve out of fractured bedrock into the very zone most drilled wells draw from - no human pollution required.

Depth matters: shallow and dug wells (25-100 ft) draw young, lightly filtered water and are most exposed to the surface pathways, while deep drilled wells (100-300+ ft) trade surface risk for bedrock chemistry - arsenic, uranium, and radon. You can see how deep wells are drilled around your property on our interactive well map. Whatever the depth, keep the wellhead environment clean: storing paint, fertilizer, or motor oil near the casing, or letting snow and leaves pile against it, invites exactly the seepage shown above.

Strips are for screening. Health decisions require an accredited laboratory - here is exactly where the line sits.

The trap with DIY kits is not the $20 you spend - it is what you do next. Kits cannot detect contaminants at the microgram and nanogram levels where EPA health limits sit, so a "clean" strip can hide a real arsenic or PFAS problem, and a crude color reading can push you into buying thousands of dollars of treatment equipment you do not need. A certified lab result costs more up front but guarantees you treat exactly what is in your water - nothing more, nothing less. If you go the mail-in route, our well water test kit comparison breaks down the certified-lab kits worth buying in 2026.

The EPA does not test residential wells on request - you source the lab. Three ways to find testing near you, and the sampling protocol that keeps your results valid.

Finding a state-certified laboratory takes five minutes:

1. Your county or state health department. Every state keeps a public list of accredited labs, and many local health departments sell low-cost test kits directly - some test for free. Our state well owner guides list the agency and program for each state.
2. The EPA certification directory. The EPA publishes links to every state's lab-certification program (see sources below) - the authoritative path to an accredited lab anywhere in the country.
3. Mail-in certified services. Certified-lab networks mail rigorous sampling kits to your door and email results with plain-English interpretation - the same accredited-lab accuracy without the drive. Our well water test store curates panels sized for private wells, from the annual baseline to full PFAS screening.

Collection technique directly changes your results. It is DIY-safe, but follow the protocol exactly:

1. Pick the right tap. Use a cold-water faucet close to the wellhead - ideally an indoor, threadless sample tap. Avoid swing-arm kitchen faucets if you can.
2. Remove the aerator. The little screen on the faucet tip harbors bacteria and debris that will contaminate a bacteria sample.
3. Sterilize the faucet. For bacteria tests, wipe the rim inside and out with isopropyl alcohol.
4. Flush 3-6 minutes. Purge the stagnant water in your plumbing and pressure tank so you sample the aquifer, not the pipes. Exception: lead and copper need a first-draw sample - the very first water out of a tap that sat overnight - because the plumbing is exactly what you are testing.
5. Fill without touching. Do not touch the inside of the lab-provided bottle or cap. If the bottle has powder or liquid inside, leave it - it is a required preservative.
6. Chill and deliver fast. Cap tightly, label, refrigerate, and get bacteria samples to the lab on ice within 24-30 hours or they will be rejected.

Lab reports bury the answer in acronyms. Three columns tell you everything.

When the report arrives, read it in this order:

1. Find the result column. This is the concentration actually found in your sample, in mg/L (parts per million), ug/L (parts per billion), or ng/L (parts per trillion). Watch the units - arsenic limits are in ppb while nitrate limits are in ppm, a thousand-fold difference.
2. Compare against the MCL or SMCL column. The report prints the EPA health standard (MCL) or aesthetic standard (SMCL) next to each result. Below the limit: monitor on schedule. Above it: act (next section).
3. Check for ND and DLR. "ND" (non-detect) or a result below the "DLR" (detection limit for reporting) means the instruments could not find the contaminant in concerning quantities - that is a pass.

A failed test is an action list, not a catastrophe. Bacteria you can usually fix yourself this weekend; chemicals need hardware.

If bacteria failed: the standard cure is shock chlorination - a one-time, massive chlorine dose that sanitizes the casing, pressure tank, and plumbing. The short version: mix about 3 pints of plain 8.25% household bleach per 100 gallons of standing system water, pour it into the casing, recirculate with a garden hose until you smell chlorine at the casing, draw it through every fixture in the house, let it sit 12-24 hours, then flush to a safe drainage area and retest in 1-2 weeks. Our step-by-step shock chlorination guide covers dosing, safety gear, and flushing in full. If bacteria return after a correct shock, the well has a structural problem - a cracked casing, failed seal, or contaminated aquifer - and it is time to call a licensed well contractor and consider continuous UV disinfection.

If a chemical failed: permanent contaminants need installed treatment matched to the specific chemical - the master table above lists the right technology per contaminant. The three workhorses:

• Reverse osmosis (RO) forces water through a membrane that physically rejects dissolved contaminants - the best general defense against nitrates, arsenic, uranium, lead, and PFAS at the kitchen tap.
• Ion exchange swaps harmless ions for dangerous ones on resin beads - softeners for hardness, specialized anion resins for nitrates and uranium.
• Granular activated carbon (GAC) adsorbs organic chemicals into millions of microscopic pores - the tool for VOCs, pesticides, and PFAS.

To match treatment to your test results in detail - including UV, aeration, softeners, and how technologies combine into a stack - see our full well water treatment guide.

One expensive mistake worth flagging: a UV disinfection lamp installed on hard or iron-rich water fails silently. Minerals coat the quartz sleeve, block the light, and let live bacteria through - UV always needs sediment filtration and softening ahead of it in the plumbing sequence.

Labs bundle individual tests into packages. Match the package to your risk profile - then check the free state programs below before paying.

If a test fails, treatment is the bigger line item - which is exactly why accurate lab numbers matter before you buy anything:

Several states use EPA, USDA, and state funds to test private wells for free - and a few will pay thousands toward treatment when a test fails.

Before paying a commercial lab, check whether your state already funds testing. These are the standout programs as of June 2026 - and even outside these states, county health departments frequently subsidize the basic bacteria/nitrate panel.

Rules and well regulations differ sharply by state - our state-by-state well owner guides cover testing requirements, well codes, and local programs for all 50 states.