How to Read Your Well Water Test Results (2026 Interpretation Guide)

A well water test report lists what the lab looked for, your result, and a limit to compare it with. The chart on this page gives that limit for every number on a typical well report, who set it, and what to do when yours is over. When someone calls me with a report, the first things I ask for are the pH, the hardness and the iron.

Caller "I guess I was just looking for somebody to walk me through what the results meant to me."

Aidan "What's the pH, hardness, and the iron?"

A caller in May, with a lab report that had just come in by email. This page is the long version of that walk-through.

Well water test results chart

Each row is one line on your report: the limit it is judged against, who set it, what a result over it means, and where to go next. A result over a health limit is about what you drink; a result over a nuisance limit is about stains, smell, taste and scale.

Of the 336 well tests my customers ran through our complete test kit from May 20 to September 28, 2026, 61 (18%) had at least one number over an EPA health limit. Lead, copper, E. coli and arsenic came up most. Coliform bacteria turned up in 135 of 331 (41%), and hard water in 148 (44%).

Sources: EPA's primary and secondary drinking water standards, its 2018 health advisory tables, its lead rule and its sodium advisory; the Connecticut Department of Public Health for hydrogen sulfide; New Jersey and New Hampshire for arsenic. All fetched September 28, 2026. EPA proposed in May 2026 to keep the PFOA and PFOS limits and drop its other PFAS limits; the 2024 limits stand until that is final.

Understanding Units on Your Water Test Report

mg/L and ppm are the same thing, µg/L and ppb are the same thing, and 1 ppm is 1,000 ppb. So an arsenic result of 10 ppb is 0.010 mg/L, which is right at the EPA limit.

A "<" result is only as useful as the number after it. On 70 of the 336 reports my customers got back, iron came back as "<2 mg/L". That does not mean there is no iron. It means under 2, and iron starts staining at 0.3.

The limits come in four kinds. None of them is a law for a private well; EPA says private wells are not regulated under the Safe Drinking Water Act, so for a well they are the line to compare against.

• An EPA limit (the MCL, maximum contaminant level) is the legal line for public water, set for health.
• An action level is the same idea for lead and copper.
• A nuisance limit (EPA's secondary standard, SMCL) covers taste, smell and stains, and EPA says it is not a health risk at that level.
• A health advisory is EPA's estimate of a level that is safe to drink over a lifetime, with no rule behind it.

A few states set a tighter number. New Jersey and New Hampshire hold arsenic to 5 ppb, and the Minnesota Department of Health uses 0.1 mg/L of manganese when a baby drinks the water.

Which problem to fix first

Anything over a health limit comes first; for the equipment, the iron filter goes ahead of the softener and the UV light goes last.

1. Health numbers. Bacteria, nitrate, arsenic, lead and the other health rows in the chart are about what you drink. Start there.
2. pH. If your pH is low, an acid neutralizer goes in too, and I set its place from your test.
3. Iron, manganese and sulfur. One iron filter handles all three.
4. Hardness. The softener goes after the neutralizer, because the neutralizer makes the water a little harder.
5. Bacteria. The UV light goes last, once the iron and hardness are out of the water.

I go through each number and its fix in this short video.

The full reasoning, with the sediment filter in front, is in the correct order for well water treatment systems.

Need help reading your report?

Text me a photo of your report

Send the page with the numbers on it. Aidan reviews water tests 7 days a week and will tell you exactly what treatment (if any) your water needs, with no obligation to purchase.

Text Aidan443-277-2204 Call800-460-5810Aidan

8 AM to 5 PM Eastern, seven days a week. A real person, not a call center.

What your iron number means

Iron starts to stain at 0.3 mg/L (0.3 ppm), which is EPA's nuisance limit, not a health limit. As I say in the video, "At 0.3 milligrams per liter, iron starts to stain and needs to be treated."

Up to about 1 ppm of clear-water iron with hard water, the softener you need anyway takes care of the iron too. Above that, I recommend the Fleck 2510AIO with Katalox Light, which removes up to 30 ppm of iron. If your pH is under 7 as well, an acid neutralizer goes in too, and I set its place from your test. The methods are compared in how to remove iron from well water.

What your hardness number means

Water over 7 grains per gallon (120 mg/L) is hard, and 7 is where appliance manufacturers recommend a water softener. If your report gives hardness in mg/L, divide by 17.1 to get grains per gallon. There is no EPA limit for hardness.

The median hardness in my customers' well tests was 5.8 gpg, and 148 of 336 (44%) were over 7. If you also need an acid neutralizer, plan the softener after it, because the neutralizer adds 3 to 6 grains per gallon of hardness. The size depends on your hardness and your household; see what size water softener you need.

What your pH number means

A pH of 7.0 is neutral, and below 7.0 the water is acidic and corrodes copper pipes and fixtures. EPA's nuisance range is 6.5 to 8.5. Below it the water can taste bitter and metallic; above it, it can feel slippery and taste like soda.

Of my customers' well tests, 64 of 336 (19%) came back below 7.0 and 29 (8.6%) below 6.5. The Clack 2.5 cubic foot non-backwashing neutralizer handles pH 5.5 to 6.9 with plain calcite; below that, I tell people to mix in FloMag (magnesium oxide, a stronger pH raiser). Everything else is in how to fix acidic well water.

What your manganese number means

Manganese stains black at 0.05 mg/L, and 0.3 mg/L is EPA's lifetime health advisory. It works just like iron: it stains toilets, showers and laundry, only blackish gray instead of orange.

Of my customers' well tests, 81 of 336 (24%) were over 0.05 and 24 (7.1%) over 0.3. The same Katalox Light iron filter removes up to 15 ppm of manganese. In the results video above I said manganese starts to stain at 0.5; the EPA line is 0.05. Testing it, and what your result means, is in how to test for manganese in well water.

What your sulfur number means

You want zero hydrogen sulfide; most people smell it at 0.5 mg/L, and at 1 ppm and above it has to be treated. It is the rotten egg smell. There is no federal limit for it.

Our complete well test does not measure hydrogen sulfide; its sulfate number is a different thing and is not the smell. For sulfur we use the same iron filter, which removes up to 10 ppm. Where the smell comes from, and what your level means, is in hydrogen sulfide in well water.

What a positive bacteria test means

Bacteria results read present or absent, and any coliform present means something is getting into your water. E. coli present means the water may be contaminated with human or animal waste.

From what I've found, a lot of the time the cap on the well casing is loose or not airtight. Insects and rodents get in, fall down the well and decay, and the bacteria grow in the water. When it keeps coming back, the fix is a UV light like the Viqua VH410, installed last, after the iron and hardness are out of the water.

What your total dissolved solids number means

TDS over 500 mg/L is over EPA's nuisance limit, and it tells you how much is dissolved in the water, not what it is. The median TDS in my customers' well tests was 244 mg/L, and 56 of 336 (17%) were over 500.

TDS is the total of everything dissolved, so look at the rows that make it up. Once you get to 500 and above, the only way to really bring TDS down is reverse osmosis, for the water you drink and cook with. What a meter reading can and cannot tell you is in TDS meter for water: what it tells you.

Frequently asked questions