Private well water
Private well-water testing: start with why you are testing, then keep a result you can use.
Choose tests for your reason for testing, recent well events, and state or local guidance. Keep the full result, including what was tested, the units, where the sample came from, and the laboratory.
On this page (10)
Start with why you are testing now.
Are you doing a routine check, responding to a change in the water, or testing after a flood or repair? The reason helps you choose tests and find the relevant local guidance.
CDC and EPA both provide broad private-well testing guidance, but they also direct well owners to state or local health and environmental authorities for concerns that depend on location. A routine check, a flood, a repaired well, a new odor, and a known local contaminant concern are not interchangeable testing jobs.
Why are you testing?
Use the row that best matches the current situation. Check whether you need a new test, help interpreting an existing result, or local testing guidance.
- Reason / context
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Routine or baseline check
No specific new event is driving the question.
What it changes: Use national guidance as a baseline, then check whether state or local guidance adds location-specific analytes, timing, or laboratory requirements.
What to check next: What does your state or local health department recommend? Check for additional local testing recommendations.
- Reason / context
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New taste, color, or odor
The water has materially changed.
What it changes: A current change can justify testing or investigation, but the symptom does not identify the contaminant by itself.
What to check next: Which test or result fits this specific change? Record the symptom and when it started, then use the relevant problem guide or local health/environmental guidance.
- Reason / context
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Flooding or another well-impact event
Recent event may affect well safety.
What it changes: Event-specific health or environmental guidance can control the immediate testing and well-safety question.
What to check next: What do the applicable state or local authorities require after this event? Ask your local health department or laboratory which tests are needed after flooding.
- Reason / context
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Well repair or component replacement
The system has changed.
What it changes: EPA and CDC identify well-system repair or replacement as a reason to test again.
What to check next: What follow-up testing or instructions apply to this repair? Follow the laboratory and local health or environmental instructions for sample collection, disinfection, and retesting.
- Reason / context
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Known local contaminant concern
Location changes the question.
What it changes: Check state and local water-quality and health guidance, including known groundwater concerns, before choosing a standard test panel.
What to check next: What contaminant or groundwater concern is documented locally? Use current local guidance and data rather than substituting a national checklist.
- Reason / context
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Known household problem
Iron, particles, a microbial result, or another defined issue is already present.
What it changes: Choose tests that match the problem you are investigating instead of adding unrelated tests by default.
What to check next: Which result do you need to investigate this problem? Use a usable result on the problem-specific page after testing.
- Reason / context
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Existing recent laboratory result
You may already have the result.
What it changes: You may need help understanding the result rather than another test.
What to check next: Is the result current, interpretable, and from the right sample point? A current, complete result may make another test unnecessary.
Start with national guidance, then check local testing advice.
CDC gives a broad national baseline that includes annual testing for total coliform bacteria, nitrates, total dissolved solids, and pH. The same guidance tells private-well users to ask state or local health or environmental departments what other germs or chemicals matter where they live.
EPA likewise recommends testing after meaningful changes such as flooding, nearby land disturbance, well-system repair, or a noticeable change in water quality. Those event triggers are useful national principles.
- Baseline question
What routine testing is appropriate for a private well, and what additional local concerns apply here?
- Event-driven question
Did a flood, repair, land-use change, new symptom, or other event create a different testing need?
- Problem-driven question
Are you investigating iron, sediment, a microbial result, hardness, odor, or a known contaminant?
A test result is useful only when you keep what was tested, the units, where the sample came from, and who performed the test.
“My result says 3.2” is not enough to interpret a water test. Keep the number with the substance tested, the units, and where the sample came from.
EPA notes that private-well results should include the concentration of the substances tested. For consequential drinking-water decisions, the laboratory, units, sample context, and any relevant method or reporting notation can be just as important as the number itself.
Keep these result details together
Keep the report details needed to understand your particular result.
- What was tested
Keep the name of each substance, organism, or water-quality measure next to its result.
- Numerical result and units
Keep the original reported value and units together. Do not silently convert away the source result.
- Detection / reporting notation
Keep less-than signs, non-detect notation, reporting limits, qualifiers, and other lab notes when they affect how the result should be read.
- Sample date and location
Record when and where the sample was collected so the result can be matched to the current water condition.
- Untreated or treated water
Know whether the sample represents raw source water, water after an existing device, or another intentional sampling point.
- Laboratory name / information
For consequential drinking-water decisions, retain the laboratory and applicable certification or accreditation context.
- Test method / result notes
Keep test-method or result notes when they materially change what the number means or how it can be compared.
Where the sample came from can change what the result answers.
A raw-well sample and a sample taken after a softener, iron system, sediment filter, carbon unit, UV system, or other treatment device answer different questions. Record whether the sample was taken before or after existing treatment.
Collection protocol is test-specific. EPA guidance tells well owners to contact the laboratory before sampling and to follow the laboratory's bottle, storage, timing, and handling instructions. Do not improvise flushing time, preservation, bottle type, transport temperature, or stabilization requirements.
- Raw source water
Useful when the job is to characterize what the well is supplying before treatment.
- After existing treatment
Useful when the job is to evaluate water after a specific treatment stage or verify downstream performance.
- One fixture / another point
Can be appropriate when a local or test-specific question calls for that sampling point. Follow the test authority's instructions rather than assuming one universal location.
Use a test that is reliable enough for what you need to know.
Simple screening can help you decide what to investigate, but it may not be enough when a health question, regulatory comparison, or treatment choice depends on a reliable concentration.
EPA and CDC direct private-well users toward state-certified drinking-water laboratories. The exact laboratory method and collection instructions still have to fit the analyte being investigated.
- Evidence type
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Screening / preliminary result
Can help you decide whether a more specific test is needed.
A preliminary screen may not be precise enough to assess a health concern or choose treatment.
- Evidence type
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Laboratory result
Becomes more important when health interpretation matters, a threshold or concentration must be interpreted, a microbial result is consequential, or treatment selection depends on an exact measurement.
Check that the sample came from the right place and that the method and units suit the question you are investigating.
When to retest depends on what changed and the instructions for that situation.
Retest when the old result no longer represents your water or when your laboratory or health department calls for confirmation. The timing depends on the situation.
- Retest trigger
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A meaningful well event occurred
Flooding, repair, replacement, or another material change can make an older result insufficient for the present condition.
- Retest trigger
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Treatment changed and performance needs verification
Know whether the verification sample should be upstream or downstream of the device and follow the applicable protocol.
- Retest trigger
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The sample or result no longer answers the current question
If the result is old, came from the wrong sample point, lacks units, or no longer represents the water, collect a new result that answers the current question.
- Retest trigger
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Public-health guidance requires confirmation
Follow the retesting instructions from your laboratory or local health department.
After flooding, repairs, or other specific events, use current guidance from your state or local authority.
Private wells are not regulated like public water systems under the federal Safe Drinking Water Act. EPA and CDC therefore direct well owners toward state and local programs, health departments, environmental agencies, and state-certified laboratories for location-specific testing and interpretation.
This matters when the question is local by nature: a regional contaminant concern, a flood, nearby land use, certified-lab resources, or an event-specific well instruction. Follow the guidance for your state or locality.
- State private-well guidance
Use for state-specific routine practices, program requirements, and well-owner resources.
- Local health / environmental guidance
Use when local contaminants, recent events, or area-specific groundwater concerns determine what should be tested.
- Certified laboratory instructions
Use the laboratory instructions for the required sample container, collection method, storage, transport, and analysis.
- Event-specific public-health guidance
Use after flooding, contamination events, well damage, or other conditions where current public-health instructions control the next step.
Once you have a usable result, use it to decide what water problem needs attention.
Use the result to decide what to do next. You may need help interpreting it, a follow-up test, or one of the guides below.
The correct next step can still be no new test.
You may not need another test if your existing result is current, complete, and from the right sample point. Use it to understand the problem. When it is missing or no longer represents the water, arrange the specific test you need.
Common private-well testing questions
Is there one test panel every private well should use?
No single panel answers every private-well question. CDC provides a broad annual baseline, while state or local guidance, well events, symptoms, geology, and known contaminant concerns can change what else should be tested.
Should I test again after well repair?
EPA and CDC identify well-system repair or replacement as a reason to retest or refresh the water result. Follow the procedure given by your laboratory or the relevant health or environmental authority.
Can I use a home strip instead of a laboratory?
A preliminary screen can help you decide what to investigate. For health concerns, microbial results, or treatment that depends on an exact concentration, you may need a state-certified laboratory and a procedure suited to the substance being tested.
Why does it matter whether I sampled before or after treatment?
Those samples answer different questions. A raw-water result characterizes what the well supplies; a post-treatment result may be used to evaluate water after an existing treatment stage. Keep the sample position with the result.
Does a positive microbial result mean I should install UV?
Not automatically. A microbial result can require public-health interpretation, well investigation, retesting, or a disinfection treatment question. The exact action depends on the result and applicable guidance.