What Contaminants Should You Test for in Water

Written by Craig "The Water Guy" Phillips

If you have a private well, you're fully responsible for your water's safety — no agency is monitoring it for you. At minimum, test annually for total coliform bacteria, nitrates, total dissolved solids (TDS), and pH. Depending on your local environment, you may also need to test for arsenic, PFAS, or volatile organic compounds. Understanding what's in your water — and what to do about it — starts with knowing exactly where to look.

Key Takeaways

• Test annually for total coliform bacteria, nitrate, total dissolved solids (TDS), and pH as core well water contaminants.
• Nitrate levels above 10 mg/L as nitrate-nitrogen are dangerous for infants and require immediate action.
• Add arsenic, PFAS, or VOC testing when nearby agriculture, industry, or landfills suggest potential contamination.
• Test immediately after flooding, well repairs, or any visible changes in water appearance or odor.
• Increase testing frequency if a pregnant person, infant, or immunocompromised individual uses the water supply.

Why Your Well Water Isn't Tested or Protected by Default

If you own a private well, you're largely on your own when it comes to water safety. The U.S. EPA's drinking water regulations only cover public water systems—your well falls completely outside that protection. No government agency monitors your tap, treats your water, or enforces safety standards on your behalf.

That responsibility lands entirely on you. Most experts recommend testing at least annually for total coliform bacteria, nitrates, total dissolved solids, and pH. Your local health or environmental department won't automatically test your well, but they can connect you with certified labs and help you interpret results.

Understanding this gap matters because agricultural runoff, leaking storage tanks, and natural geologic sources can silently contaminate your aquifer—with no centralized system to catch it.

Well Water Contaminants You Should Always Test For

So what should we actually be testing for? Start with four non-negotiables: total coliform bacteria, nitrate, total dissolved solids (TDS), and pH.

Coliform bacteria act as your canary—they signal whether harmful microbes have infiltrated your water. Test annually, and immediately after flooding, repairs, or any visual changes.

Nitrate is especially critical if infants drink your water. Levels above 10 mg/L nitrate-nitrogen trigger methemoglobinemia, a dangerous oxygen-deprivation condition in babies.

TDS reveals your water's overall mineral load, flagging potential corrosion or contamination you'd otherwise miss. pH works similarly—values outside 6.5–8.5 accelerate pipe corrosion, leaching lead and copper directly into your glass.

Beyond these four, layer in targeted tests based on your local environment—agriculture, industry, landfills, or known regional contamination each demand specific additions like arsenic, PFAS, or VOCs.

How to Get Your Well Water Tested the Right Way

Getting well water tested correctly starts with timing and who you hire. Inspect your well mechanically every spring, and collect water samples after floods, nearby land disturbances, well repairs, or any changes in taste, color, or smell.

For lab testing, use a state-certified laboratory—your local health or environmental department can point you toward one. Test at least annually for total coliform bacteria, nitrates, total dissolved solids, and pH.

When sampling, follow the lab's instructions precisely: use their provided bottles, disinfect taps if required, sample from the correct location (typically your kitchen tap without aerators), and complete all chain-of-custody forms.

Before interpreting results, confirm the report's units match your guideline's units. If anything's unclear, contact your local health department directly.

How to Read Your Well Water Test Results

Once your test results arrive, the first thing we need to do is make sure we're comparing apples to apples—every number on the report comes with units, and those units have to match whatever guideline we're checking against. Nitrates, for example, are measured in mg/L as nitrogen, with the EPA's MCL sitting at 10 mg/L. TDS above 500 mg/L signals taste and scaling issues. pH outside the 6.5–8.5 range can mobilize metals like lead and copper through corrosion.

Any positive total coliform or E. coli reading—regardless of how small—means we switch to bottled water immediately and contact a certified lab. For PFAS, VOCs, arsenic, or radionuclides, we compare results against state and EPA health-based guidelines and loop in our local health department.

How Often Should You Test Your Well Water?

Knowing how to read our results is only half the battle—the other half is making sure we're testing often enough to catch problems before they affect our health.

At minimum, we should test annually for total coliform bacteria, nitrates, TDS, and pH.

Every spring, we'll also want a mechanical inspection and water test.

But certain situations demand more frequent testing—quarterly or after contamination events.

If someone in our household becomes pregnant, an infant moves in, or a resident becomes immune-compromised, we increase our testing cadence immediately.

The same applies after flooding, nearby land disturbance, repairs, or borderline previous results.

Always use a state-certified lab, and contact our local health or environmental department for guidance on additional contaminants like PFAS or VOCs specific to our region.

Frequently Asked Questions

What Are the 5 Physical Tests for Water?

We recommend testing pH, total dissolved solids (TDS), turbidity, temperature, and color/odor. These five physical tests reveal critical baseline conditions that'll help us identify corrosion risks, contamination signals, and treatment needs before problems escalate.

What Are the Common Contaminants Tested by Water Testers?

We commonly test for total coliform bacteria, E. coli, nitrates, lead, arsenic, copper, VOCs, pesticides, and emerging PFAS "forever chemicals"—each targeting specific health risks tied to microbial, chemical, or industrial contamination sources.

What Are the 5 Worst Bottled Waters?

We can't rank the 5 worst bottled waters definitively, but brands showing elevated microplastics, arsenic, antimony leaching, or bacterial contamination in independent tests—like some regional spring waters—deserve your closest scrutiny before purchasing.

What Are the 5 Main Indicators of Water Quality?

We recommend testing for these 5 key water quality indicators: total coliform bacteria, nitrate levels, total dissolved solids (TDS), pH balance, and E. coli/fecal coliforms—they'll reveal contamination risks, mineral content, and overall safety.