Well Water Test Results Checker
Type in the numbers from your lab report to see which results are above EPA health or cosmetic reference levels, what each one means, and what to do next. The checker converts units for you, including the nitrate-as-N and nitrate-as-NO3 mix-up that trips up many well owners.
Any results and directions from these calculators are estimates for planning. Confirm them with a licensed testing facility before you act on them.
- 30+ common well tests
- Nothing is uploaded or stored
- Works on your phone
- No sign-up
Enter your lab results
Fill in only the results your report shows. Type ND for "not detected" or a value like <0.5 if the lab reports "less than."
Educational information only. Reference levels are federal values; your state may apply different or additional standards. Read your report with your certified laboratory or local health department before acting. See our water safety disclaimer.
How to use the well water test results checker
Have your laboratory report in front of you. For each result it lists, find the matching line in the checker, type the number, and choose the unit printed on the report. You do not have to fill in everything. Most private well reports cover only a handful of tests, often total coliform, E. coli, nitrate, and a few minerals such as iron, hardness and pH. Leave everything else blank.
- Start with bacteria. Set total coliform and E. coli to "Absent" or "Present." If your lab gives a count per 100 mL instead, any count above zero counts as present.
- Match the units exactly. The same arsenic result might be printed as 0.012 mg/L or 12 µg/L. Pick the unit your report uses and the checker converts it.
- Tick the household boxes if they apply. Nitrate, manganese and sulfate guidance is stricter for infants, and sodium matters for low-sodium diets.
- Press "Check my results." Results are sorted with the most urgent first. Each card shows your value, the reference level, a simple gauge, and a plain-English explanation.
Want to show a spouse, landlord, buyer or well contractor? Use Copy a link to these results. The numbers are stored after the # in the link, a part of the address browsers keep on your device and never send to our server.
How the checker sorts your results
Private wells are not covered by the federal Safe Drinking Water Act, so there is no legal limit that applies to your well. The limits written for public water systems are still the most widely used benchmark, and that is what the checker compares against. Every result lands in one of these groups:
| Label | What it means |
|---|---|
| Act now | Bacteria were found, or nitrate or nitrite is above the reference. These can cause illness from short-term exposure, so use a known-safe water source for drinking while you get local guidance. |
| Above health reference | The value is above an EPA Maximum Contaminant Level (MCL), action level or health advisory. Most of these references are about years of drinking, not one glass. Confirm the result and plan a response. |
| Worth a closer look | Below the reference but at least half of it, any detectable lead, any synthetic chemical, or a "not detected" result where the lab's reporting limit was too high to be useful. |
| Taste, stain or equipment | Above an EPA secondary level. These are about staining, taste, odor, scale or corrosion, not health. |
| Within reference | Below the reference level for that test. |
The checker also looks for patterns across results, because a single number rarely tells the whole story. Low pH with copper or lead points to corrosive water. Iron together with hardness changes how a softener must be sized. Coliform bacteria together with elevated nitrate often suggests surface water, septic or manure influence.
Units on a well water report: mg/L, ppm, ppb, ppt and gpg
Lab reports use several units, sometimes on the same page. They differ by factors of a thousand, so a misread decimal can make a result look a thousand times better or worse than it is.
- mg/L (milligrams per liter) is the same as ppm (parts per million) for water. Iron, nitrate, hardness and most minerals are reported this way.
- µg/L (micrograms per liter) is the same as ppb (parts per billion). 1 mg/L = 1,000 µg/L. Arsenic, lead and uranium are often reported in ppb.
- ng/L (nanograms per liter) is the same as ppt (parts per trillion). 1 µg/L = 1,000 ng/L. PFAS results use ppt.
- gpg (grains per gallon) is used only for hardness. 1 gpg = 17.1 mg/L as calcium carbonate. Softener dealers use gpg; labs usually use mg/L.
- pCi/L (picocuries per liter) measures radioactivity and is used for radium, gross alpha and radon.
The nitrate unit trap: "as N" versus "as NO3"
Nitrate can be reported as the weight of the nitrogen in it (nitrate-N or NO3-N) or as the weight of the whole nitrate ion (NO3). The EPA limit of 10 mg/L is expressed as nitrogen. The same water reported as the nitrate ion reads about 44 mg/L. A reading of 30 mg/L "nitrate" could therefore be comfortably under the limit (if reported as NO3, about 6.8 mg/L as N) or three times over it (if reported as N). Check the column heading or footnotes on your report, then pick the matching unit in the checker. If the report does not say, ask the lab.
"ND," reporting limits and "less than" results
"ND" means the lab did not detect the substance above its reporting limit, the smallest amount its method can reliably measure. It does not mean zero. A result written as "<0.005 mg/L" means the same thing with the limit shown. Enter these as ND or as the "less than" value and the checker handles them correctly. If the reporting limit itself is higher than the health reference, for example arsenic reported as "<0.02 mg/L" when the reference is 0.010 mg/L, the checker flags it, because that result cannot confirm the water is below the reference. For more on reading a report, see how to read well water lab results.
Reference levels used by the checker
These are the U.S. EPA values the checker compares against, current as of September 29, 2026. MCLs are enforceable for public water systems; secondary levels are non-enforceable guidelines for taste, odor and appearance.
| Test | Reference | Type |
|---|---|---|
| Total coliform, E. coli | Absent | Health (goal of zero) |
| Nitrate (as N) | 10 mg/L | MCL |
| Nitrite (as N) | 1 mg/L | MCL |
| Arsenic | 0.010 mg/L (10 ppb) | MCL |
| Lead | 0.010 mg/L (10 ppb) | Action level (health goal: zero) |
| Copper | 1.3 mg/L | Action level (secondary: 1.0) |
| Fluoride | 4.0 mg/L | MCL (secondary: 2.0) |
| Manganese | 0.3 mg/L | Health advisory (secondary: 0.05) |
| Uranium | 0.030 mg/L (30 ppb) | MCL |
| Radium 226 + 228 | 5 pCi/L | MCL |
| Gross alpha | 15 pCi/L | MCL |
| Barium · Selenium · Chromium | 2 · 0.05 · 0.1 mg/L | MCL |
| Cadmium · Mercury · Antimony | 0.005 · 0.002 · 0.006 mg/L | MCL |
| PFOA · PFOS | 4.0 ppt each | MCL (2024 rule; retained in 2026 proposals) |
| Benzene · TCE · PCE | 0.005 mg/L | MCL |
| Atrazine | 0.003 mg/L | MCL |
| Iron | 0.3 mg/L | Secondary |
| pH | 6.5 – 8.5 | Secondary |
| Sulfate · Chloride | 250 mg/L | Secondary (sulfate health advisory: 500) |
| Total dissolved solids | 500 mg/L | Secondary |
| Zinc · Aluminum | 5 · 0.2 mg/L | Secondary |
| Sodium | 20 mg/L | Guidance for sodium-restricted diets |
| Hardness | No standard | Classified soft to very hard (USGS) |
Several states set their own, sometimes stricter, values, especially for PFAS, manganese and hexavalent chromium. When a state value exists, it is the one to use.
After you check your results
- Bacteria present? Inspect the wellhead, then disinfect. Our well shock chlorination calculator works out the bleach amount and tracks the 12-hour hold.
- Hard water or iron? The water softener size calculator uses your hardness, iron and manganese results. When you use the checker first, the calculator link carries your numbers over.
- Above a health reference? Retest to confirm, then compare treatment categories using the confirmed result, not a symptom.
- Everything within reference? Keep testing on schedule. See the annual well testing guide.
- Missing tests? Use the water testing guide to plan what your area calls for.
Frequently asked questions
Is my well water safe if everything is within the reference levels?
It means nothing you entered exceeded a reference level. It cannot speak for contaminants that were not tested, and a well can change after heavy rain, flooding, nearby construction or repairs. Many health-related contaminants have no taste, color or odor, which is why regular testing matters.
What EPA standards apply to private wells?
None are legally required. EPA's drinking water standards apply to public water systems. Private well owners are responsible for their own water, and health departments generally recommend comparing well results with the public drinking water standards, as this checker does.
My report says nitrate is 25 mg/L. Is that over the limit?
It depends on the unit. If the report means 25 mg/L as nitrogen (nitrate-N), it is well above the 10 mg/L limit. If it means 25 mg/L as the nitrate ion (NO3), that equals about 5.6 mg/L as nitrogen, which is below the limit. Check which unit your lab uses and choose it in the checker.
What does "ND" mean on a water test?
ND means not detected: the lab did not find the substance above its reporting limit, the smallest amount its method can reliably measure. It is not proof of zero, and reporting limits differ between labs and methods.
How do I convert grains per gallon to mg/L for hardness?
Multiply grains per gallon by 17.1 to get mg/L (or ppm) as calcium carbonate. Divide mg/L by 17.1 to get grains per gallon. For example, 10 gpg is about 171 mg/L.
Is the information I type saved or sent anywhere?
No. The checker runs entirely in your browser. It makes no network requests with your numbers and stores nothing on our server. If you copy a share link, the values travel inside that link only.
Related free tools
Sources
- U.S. EPA. National Primary Drinking Water Regulations
- U.S. EPA. Secondary Drinking Water Standards: Guidance for Nuisance Chemicals
- U.S. EPA. PFAS National Primary Drinking Water Regulation and 2026 proposed compliance extension
- U.S. EPA. Lead and Copper Rule Improvements
- U.S. EPA. Drinking Water Standards and Health Advisories Tables (manganese, sulfate, sodium)
- U.S. EPA. Private Drinking Water Wells
- CDC. Guidelines for Testing Well Water
- USGS. Hardness of Water