Understanding Your Well Test Results
A lab report is not a simple pass/fail. Here's how to read one before deciding on next steps.
Short answer: Compare each reported analyte against the applicable comparison value (an EPA MCL used as a reference point, a health-based guideline, or a treatment threshold), note the unit, and understand what the test can and cannot tell you before choosing treatment.
How to read a result table
| Field | What to check |
|---|---|
| Analyte | Exactly what was tested — e.g., total coliform vs. E. coli are different results. |
| Reported result | The measured value, including whether it's "non-detect" and at what detection limit. |
| Unit | mg/L, µg/L, ng/L, or ppt — confirm you're comparing like units. |
| Comparison value | Which standard is being referenced, and whether it's enforceable or advisory. |
| Source of comparison value | EPA, NJDEP, or the lab's own reference — not all carry equal regulatory weight for private wells. |
What a test can and cannot show
A single sample reflects conditions at the time of collection. It does not confirm results will be identical next month, does not test for every possible contaminant unless you ordered a broad panel, and does not diagnose a health condition. No result should be labeled simply "safe" or "unsafe" without this context.
Recommended next steps by result type
- Bacteria detected: follow the lab's disinfection and retesting guidance, and retest before assuming the issue is resolved.
- A chemical result above a comparison value: research treatment options matched specifically to that contaminant, and retest after installing any system.
- All results below comparison values: maintain your routine testing calendar rather than assuming no further testing is needed.
Official sources
- U.S. EPA drinking water standards and health advisories
- NJDEP Private Wells program
Related
My result is above an EPA guideline — is my well "unsafe"?
Private wells aren't legally bound by public-system MCLs, but EPA and NJDEP reference values are useful benchmarks. Discuss elevated results with the testing lab or a qualified water-treatment provider to understand appropriate next steps for your specific contaminant and level.
This page provides general educational information and is not medical or laboratory advice.
Last reviewed: 2026-07-11. Report a correction.