The EPA says private well owners should test their water at least once a year. Most don’t.

That gap matters because private wells have no regulatory oversight. Municipal water systems are tested constantly and the results are public. Your well is yours alone. Nobody is checking it but you.

About 43 million Americans rely on private wells as their primary drinking water source, according to USGS data on domestic supply wells. That’s a lot of water with no mandatory testing requirements.

What to Test For

Not every well needs the same panel. Start with what your situation actually calls for.

Every year, no exceptions: total coliform bacteria, E. coli, nitrates, and pH. These are the EPA’s baseline recommendations for annual testing. Bacteria and nitrates are the two most urgent risks in most wells. E. coli indicates fecal contamination. Nitrates are colorless, odorless, and dangerous to infants at high levels.

If you’re buying a home with a well: get a full panel before closing. That means bacteria, nitrates, arsenic, lead, iron, manganese, hardness, and VOCs at minimum. You don’t want to discover an arsenic problem after you’ve moved in.

If you live near farmland: add nitrates and pesticides. Agricultural runoff is a real contamination pathway, and nitrate levels can shift seasonally near irrigated fields.

If you live in the Northeast or Southwest: add arsenic. It occurs naturally in the geology of those regions. Many well owners in New England and the Mountain West have arsenic levels above the EPA’s limit of 10 parts per billion without knowing it.

After flooding: test immediately for bacteria, nitrates, and turbidity. Floodwater can overwhelm a well casing and introduce surface contamination. Don’t wait for your annual test.

If your water tastes or smells different: add iron, manganese, and hydrogen sulfide to your panel. These aren’t typically health emergencies, but they signal something has changed underground.

If your home has old plumbing: add lead. The well itself won’t have lead, but old pipes and fittings can leach it into your water on the way to the tap.

See the EPA’s full list of potential well water contaminants and their impacts for more detail by region and land use.

Lab Tests vs. Home Test Kits

Home test strips are cheap and fast. They’re also not good enough for safety decisions.

The problem is accuracy. Home kits often miss contaminants entirely, and they can produce false negatives for the two things that matter most: bacteria and nitrates. A negative result on a home strip does not mean your water is safe. It means the strip didn’t detect anything above its detection threshold, which is not the same thing.

For a quick screen between annual tests, a home kit is fine. Our review of the best home water test kits covers which ones are worth buying for that purpose.

For results you can act on, use a certified lab. A basic bacteria and nitrate panel costs $30 to $100 at most state-certified labs. A full comprehensive panel runs $100 to $300 depending on what’s included. That’s a reasonable price to know what’s in water your family drinks every day.

Mail-in testing has gotten easier too. See our best mail-in water tests review for options that send you a sterile collection kit and provide certified lab results by email.

How to Find a Certified Lab

The EPA maintains a searchable list of certified labs by state. Go here: Find a Certified Laboratory for Testing Your Well Water.

Before you pay, check with your state health department. Many states offer free or subsidized testing for private well owners, especially for bacteria and nitrates. Call the number on your state health department’s website and ask specifically about private well testing programs. You might save yourself $50.

How to Collect a Sample

Sample collection technique matters. A contaminated sample gives you bad data, and false positives lead to unnecessary treatment or retesting costs.

The lab will send sterile containers and specific instructions. Follow them exactly. Here’s the general process for a bacteria test:

Use the container the lab provides, not one from home. Don’t use an outdoor hose spigot, use a kitchen or bathroom faucet without an aerator if possible. Let the water run for 2 to 3 minutes before collecting. This flushes the line and gives you a true sample from the aquifer, not just stagnant water sitting in your pipes. Collect the sample mid-stream without touching the container to the faucet. Cap it immediately. Keep it refrigerated and deliver it to the lab or drop it in a cooled shipping box within 24 to 48 hours.

For chemical tests, the procedure is similar but the rinse time and container type may differ. The lab’s instructions will specify.

How to Read Your Results

Your results will show a measured level for each contaminant alongside the EPA’s Maximum Contaminant Level (MCL) for that contaminant.

The MCL is the legal limit for public water systems. For private wells, it’s the benchmark to use. If your result is above the MCL, you need to act. If it’s below the MCL, your water is within the federal standard for that contaminant.

One important nuance: some contaminants have health-based guidelines that are stricter than the legal MCL. The Environmental Working Group maintains a set of health guidelines based on independent research rather than regulatory compromise. Their limits for arsenic, nitrates, and several other contaminants are tighter than EPA’s MCLs. Worth looking at, especially for PFAS, where the science has moved faster than regulation.

What to Do If Results Are High

Different contaminants call for different responses. Here’s the short version:

High bacteria or E. coli: act fast. Shock chlorinate the well with a standard household bleach procedure, your county extension office or state health department can walk you through the process. Retest two weeks after treatment to confirm the problem is resolved. Read more about bacteria in drinking water.

High nitrates: if you have infants in the home, switch to bottled water immediately. Nitrates above 10 mg/L can cause methemoglobinemia (blue baby syndrome) in infants under 6 months. Adults are not acutely at risk from the same levels, but you still want to fix it. Reverse osmosis removes nitrates effectively. Read more about nitrates in drinking water.

High arsenic: don’t drink the water untreated. Arsenic is a carcinogen and there’s no safe level for long-term exposure. A point-of-use reverse osmosis system certified to NSF/ANSI 58 for arsenic removal is the standard fix. Read more about arsenic in drinking water.

High iron or manganese: not an emergency, but it affects taste and can stain laundry and fixtures. Contact a water treatment specialist. There are multiple treatment approaches depending on the form of iron in your water.

Start Here If You’ve Never Tested

If you’ve never tested your well, don’t try to figure out the perfect panel on the first try. Start with bacteria and nitrates. Those are the two most urgent risks in most private wells. They’re cheap to test. And the results tell you whether you have a problem that needs immediate attention.

Order the basic panel this week. The EPA’s certified lab locator will show you options near you. Most labs have a turnaround of 3 to 5 business days.

Once you have those results back, you can decide what else to test for based on your location and situation. But get the baseline done first.

Sources: EPA Private Wells | EPA Certified Lab Locator | USGS Domestic Wells | EWG Health Standards