This free well water test results interpreter compares each number on your lab report with EPA drinking water limits. Got a water test report full of numbers? Type in whatever your lab measured and leave the rest blank. The interpreter compares each result with US EPA drinking water standards, flags health risks separately from nuisance issues like staining and hardness, and suggests the type of treatment that usually solves each problem.
| Parameter | Your result | Unit (mg/L = ppm, µg/L = ppb) |
|---|
Leave blank anything you did not test. Results reported as “< value” or “ND” (not detected) can be left blank or entered as 0.
How to use the Well Water Test Results Interpreter
- Find the results table on your lab report.
- Enter each result in the matching box, using the unit shown (mg/L = ppm, µg/L = ppb). Leave anything you didn’t test blank.
- Press Interpret my results, or Load example report to see how it works first.
- Check which results meet the limits and which need attention.
The well water test results interpreter is a guide. It doesn’t replace advice from your state health department or a certified lab. For testing schedules and treatment options, see EPA’s private wells guidance.
How to read a well water test report
Private wells in the US are not regulated by the Safe Drinking Water Act, so the owner is responsible for testing and treatment. Labs report results against two kinds of EPA standards:
- Maximum Contaminant Levels (MCLs): enforceable health limits for public water systems. They are the best benchmark for private wells. Exceeding one means a health risk.
- Secondary standards (SMCLs): non-enforceable guidelines for taste, odor, staining and scale. Iron, manganese, pH and hardness usually fall here.
- Action levels: lead (15 µg/L) and copper (1.3 mg/L) are controlled by action levels because they mostly come from plumbing, not the aquifer.
Key EPA limits used by this tool
| Contaminant | Limit | Type |
|---|---|---|
| Total coliform / E. coli | Absent | Health |
| Nitrate (as N) | 10 mg/L | MCL |
| Arsenic | 10 µg/L | MCL |
| Lead | 15 µg/L | Action level (goal: 0) |
| Uranium | 30 µg/L | MCL |
| Fluoride | 4.0 mg/L (2.0 secondary) | MCL / SMCL |
| Manganese | 0.05 mg/L (0.3 health advisory) | SMCL / HA |
| Iron | 0.3 mg/L | SMCL |
| pH | 6.5 – 8.5 | SMCL |
| TDS | 500 mg/L | SMCL |
How often should you test a private well?
- Every year: total coliform bacteria, nitrate, pH and TDS.
- Every 3–5 years: arsenic, lead, uranium, fluoride, manganese and other metals, plus PFAS if you live near airports, military bases, landfills or industrial sites.
- Straight away: after flooding, well repairs, a change in taste, color or odor, or if someone in the home is pregnant or has a new baby.
Use a state-certified laboratory. In the US, your state health department or county extension office can give you a list.
Frequently asked questions
What is a safe level of nitrate in well water?
The EPA limit is 10 mg/L nitrate as nitrogen (45 mg/L as nitrate ion). Water above this should never be used to prepare infant formula because it can cause “blue baby syndrome” (methemoglobinemia).
My report says ppm and ppb. How do they relate to mg/L?
For water, 1 ppm = 1 mg/L and 1 ppb = 1 µg/L = 0.001 mg/L. The interpreter lets you pick the unit for each result.
Is hard water safe to drink?
Yes. Hardness (calcium and magnesium) is not a health concern. It causes scale, soap scum and shorter appliance life. A softener fixes it, but keep one unsoftened tap for drinking if you are on a low-sodium diet.
Does boiling water make it safe?
Boiling kills bacteria such as E. coli but does not remove chemicals. It actually concentrates nitrate, arsenic, lead and other dissolved contaminants.
What does "ND" or "<" mean on my report?
ND means not detected, and “< 0.001” means below the lab’s reporting limit. You can leave these blank or enter 0.
What should I test for in well water?
Test every year for total coliform bacteria, nitrate, pH and total dissolved solids. Every few years, or if your area has known problems, add arsenic, lead, manganese, fluoride and uranium, and PFAS if you live near industry, airports or military sites.
What does nitrate as nitrogen mean?
Labs report nitrate either as nitrate-nitrogen (NO₃-N) or as the nitrate ion (NO₃). The EPA limit is 10 mg/L as N, which equals about 44 mg/L as NO₃. Multiply NO₃-N by 4.43 to convert.
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This tool gives general information based on US EPA drinking water standards (checked 2026). It is not medical advice and does not replace advice from your laboratory, local health department or a certified water treatment professional. Built by an accredited water-testing laboratory professional.