Private well water testing: understand your lab report and know who to call
General information, not medical advice. This site cannot tell you whether your water is safe. Ask your certified lab or local health department. Read the full disclaimer.
Have a report from private well water testing? Enter its numbers to see them beside EPA limits, or look up the units, ND and limits on your report.
What do you need help with?
- What do mg/L, µg/L and ppb mean on my report?
- My report says ND or <. Does that mean zero?
- Why does my nitrate result say "as N"?
- What is the difference between an MCL and an action level?
- My bacteria result says Present. What does that mean?
- How do my numbers compare with EPA limits?
- What should I ask my lab?
- How often should I test my well water?
Limits from EPA's National Primary Drinking Water Regulations, checked October 3, 2026.
Text version of the example
Example report. Made-up numbers for illustration only. The reporting limit is also made up. This example uses a reporting-limit ND convention and presence/absence bacteria testing.
- Nitrate (as N)
- Result: 2.0 mg/L. EPA MCL: 10 mg/L, measured as nitrogen.
- Arsenic
- Result: ND (<0.001) mg/L. The example reporting limit is 0.001 mg/L. EPA MCL: 0.010 mg/L.
- Lead
- Result: 0.002 mg/L. EPA action level: 0.015 mg/L. The action level becomes 0.010 mg/L on November 1, 2027.
- Total coliform bacteria
- Result: Absent. P/A means Present or Absent. No numeric limit is shown.
ND means not detected above the lab's reporting limit. It does not mean zero. Ask your lab about the notation on your own report.
Federal limits apply to public water systems, not private wells. Bacteria results say Present or Absent, not mg/L, in this presence/absence example.
Who to ask about your private well test
Ask the lab that issued your report about its results, units and notes. For questions about your household's drinking water, contact your local or state health department.
Standards, local geology and state requirements all vary. Confirm anything on this page with your state or local health department before acting on it.
Private wells and federal EPA limits
EPA's federal drinking-water standards apply to public water systems. They do not regulate private wells under the Safe Drinking Water Act.
EPA says private well owners are responsible for their household's drinking water.
Sources and check dates
Saved EPA source copies rechecked October 2, 2026. Original source checks:
- EPA: National Primary Drinking Water Regulations. Checked September 27, 2026.
- EPA: Private Drinking Water Wells. Checked September 27, 2026.
- EPA: Drinking Water From Household Wells. Checked September 27, 2026.
We have not tested any water or products.