Well water test result reader
Your lab report is a column of numbers. Type them in and we put each one next to the matching EPA drinking water standard and say what it means.
Leave blank anything your lab didn’t test. Use the units shown; 1 mg/L = 1,000 µg/L, and ppm = mg/L, ppb = µg/L.
| Test | Your result | Standard | Status |
|---|---|---|---|
| Total coliform bacteria | Should be absent (MCL goal: zero) | — | |
| E. coli | Must be absent | — | |
| Nitrate (as N) | MCL 10 mg/L | — | |
| Nitrite (as N) | MCL 1 mg/L | — | |
| Arsenic | MCL 10 µg/L (0.010 mg/L) | — | |
| Lead | Action level 15 µg/L; EPA’s 2024 rule lowers it to 10 µg/L for public systems. Goal: zero | — | |
| Copper | Action level 1.3 mg/L | — | |
| Fluoride | MCL 4.0 mg/L; secondary 2.0 mg/L | — | |
| Uranium | MCL 30 µg/L | — | |
| Manganese | Secondary 0.05 mg/L; EPA lifetime health advisory 0.3 mg/L | — | |
| Iron | Secondary 0.3 mg/L | — | |
| Total dissolved solids | Secondary 500 mg/L | — | |
| Chloride | Secondary 250 mg/L | — | |
| Sulfate | Secondary 250 mg/L | — | |
| pH | Secondary range 6.5 to 8.5 | — | |
| Hardness (as CaCO₃) | No federal standard; USGS classes | — |
Nothing flagged yet. Enter results above to compare them with EPA standards.
Private wells aren’t regulated like city water
EPA’s drinking water rules apply to public water systems. They don’t apply to private household wells. Nobody tests your well for you, and keeping the water safe is up to you. The federal standards are still the best yardstick, because they say what level of each contaminant is considered safe to drink over a lifetime. This tool uses them for that purpose.
Three kinds of limits
Maximum contaminant levels (MCLs) are health-based, enforceable limits for public systems, such as 10 mg/L for nitrate or 10 µg/L for arsenic. Action levels apply to lead and copper, which usually come from plumbing rather than the water source. Secondary standards cover taste, odor, color, staining, and corrosion, such as 0.3 mg/L for iron. They aren’t health limits, but they explain most of the everyday complaints well owners have. The status badge shows which kind of limit a result crosses: red for a health-based limit, amber for a secondary or nuisance level.
What to test for, and how often
EPA recommends testing a private well every year for total coliform bacteria, nitrates, total dissolved solids, and pH. Test more widely when you buy a home, when the taste, smell, or color changes, after a flood, after work on the well, or if someone in the home is pregnant or there’s an infant. Local geology decides what else is worth checking. Arsenic, uranium, manganese, and fluoride can all occur naturally. Your county health department usually knows which ones are common where you live. See our well water testing guide for how to take a sample and choose a certified lab.
If something is flagged
One high result is worth confirming with a second sample, but don’t wait on it before protecting your family. For bacteria, EPA and the CDC advise boiling water or using bottled water until the problem is fixed. For nitrate, don’t boil, because boiling concentrates it. Use bottled water, especially for infant formula. Then find the source. Bacteria usually point to a damaged well cap, a cracked casing, surface water getting in, or a nearby septic problem. Shock chlorination treats the well itself but doesn’t fix the way the contamination got in.
Units, briefly
Labs report in milligrams per liter (mg/L, the same as parts per million) or micrograms per liter (µg/L, the same as parts per billion). A result of 0.012 mg/L of arsenic is 12 µg/L, which is above the 10 µg/L limit. Nitrate may be reported “as N” or “as NO₃”. The 10 mg/L limit is as nitrogen, and a result reported as nitrate can be divided by about 4.43 to convert it. Hardness is sometimes given in grains per gallon. Multiply by 17.1 to get mg/L.
This tool doesn’t diagnose health risks for your household. It compares numbers with published standards. Talk to your health department or a certified water professional about treatment.