How to Read Your Well Water Test Results (2026 Interpretation Guide)
Well Water Testing & Diagnostics
How to Read Your Well Water Test Results (2026 Interpretation Guide)
A typical well water test report measures iron, hardness, pH, manganese, sulfur, bacteria, and total dissolved solids. This guide explains what every number means and what treatment (if any) you need.
Looking to get your water tested first? Our companion guide (coming soon) covers lab tests vs DIY kits and how to collect a proper sample. Already know your problem? Start with our Complete Guide to Well Water Filtration Systems.
Quick Checklist: How to Read Your Water Test
- Find the units on your report (mg/L, ppm, or gpg)
- Check pH first: below 7.0 means acidic water
- Look at iron: above 0.3 ppm causes staining
- Check hardness: above 7 gpg (120 mg/L) is hard water
- Look for manganese: above 0.05 ppm causes black staining
- Check sulfur / H₂S: any detectable level causes odor
- Look at bacteria: "present" or "positive" means treatment needed
- Check TDS: above 500 ppm may affect taste
- Send your results to Aidan at 800-460-5810 for a free interpretation
TL;DR: What Your Water Test Numbers Mean
Most lab reports list contaminants in milligrams per liter (mg/L), which equals parts per million (ppm). Hardness is sometimes reported in grains per gallon (gpg), where 1 gpg = 17.1 mg/L. Here's the quick version of what matters:
- Iron above 0.3 ppm → staining starts → treat with an iron filter
- Hardness above 7 gpg (120 mg/L) → scale buildup → treat with a water softener
- pH below 7.0 → acidic, corrosive water → treat with an acid neutralizer
- Manganese above 0.05 ppm → black staining → treat with an iron/manganese filter
- Sulfur (H₂S) above 0 ppm → rotten egg smell → treat with a sulfur filter
- Coliform bacteria: positive → health risk → treat with a UV light system
- TDS above 500 ppm → taste/quality issues → treat with reverse osmosis
Every well is different. If you have multiple issues, treatment order matters. Call Aidan at 800-460-5810 or text your water test to 443-277-2204 for a free, no-pressure recommendation.
Understanding Units on Your Water Test Report
Before interpreting any numbers, check which units your lab used. Most well water tests report results in one of three formats:
| Unit | Abbreviation | Used For | Conversion |
|---|---|---|---|
| Milligrams per liter | mg/L | Most contaminants (iron, manganese, sulfur, TDS) | 1 mg/L = 1 ppm |
| Parts per million | ppm | Same as mg/L (interchangeable) | 1 ppm = 1 mg/L |
| Grains per gallon | gpg | Hardness (calcium and magnesium) | 1 gpg = 17.1 mg/L |
mg/L and ppm are the same thing. If your report says iron is 3.0 mg/L, that's 3.0 ppm. Hardness is the one parameter that commonly uses a different unit (gpg). Some labs report hardness in mg/L, so you may need to divide by 17.1 to get gpg.
pH is measured on a scale of 0 to 14 and has no units. Bacteria is reported as "present/absent" or "positive/negative," not as a number.
Iron (Fe): What Your Numbers Mean
Iron is measured in milligrams per liter (mg/L) or parts per million (ppm). It's one of the most common well water contaminants and causes orange/reddish-brown staining on fixtures, toilets, sinks, and laundry.
The EPA's secondary maximum contaminant level (SMCL) for iron is 0.3 mg/L. This isn't a health-based limit; it's an aesthetic standard. Iron at typical well water levels is not dangerous to drink, but it creates persistent staining that gets worse over time.
Iron Ranges and What They Mean
What Removes Iron from Well Water?
The Fleck 2510AIO with Katalox Light removes up to 30 ppm of iron without chemicals. It uses air injection oxidation (AIO) combined with Katalox Light catalytic media. This is the system we've used for over 15 years with consistent results. For a deeper look at how it works and how to size one, read our Complete Guide to Iron Filters.
Important: If your test shows iron AND low pH (below 6.5), the pH needs to be corrected first with an acid neutralizer. Iron filters work best when pH is 6.5 or above. Learn more about this in our How to Remove Iron from Well Water guide.
Hardness (Calcium & Magnesium): What Your Numbers Mean
Hardness is caused by dissolved calcium and magnesium in your water. It's reported in grains per gallon (gpg) or milligrams per liter (mg/L). To convert mg/L to gpg, divide by 17.1.
There is no EPA health limit for hardness because it's not a health concern. It's a practical concern: hard water creates white scale buildup on fixtures, reduces soap effectiveness, shortens appliance life, and leaves spots on dishes and shower doors.
Hardness Ranges and What They Mean
(0 - 50 mg/L)
(50 - 120 mg/L)
(120 - 170 mg/L)
(170 - 256 mg/L)
(256+ mg/L)
What Removes Hardness from Well Water?
The Fleck 5600SXT 48,000 Grain Water Softener uses ion exchange to remove calcium and magnesium from the water. It's salt-based, digitally controlled, and sized for most 2-4 bathroom homes. For sizing help and more details, see our Complete Guide to Water Softeners.
Note: If your test also shows iron, a water softener alone won't solve both problems. Iron clogs softener resin over time. You'll need an iron filter before the softener. Read Can a Water Softener Remove Iron? for the full explanation.
pH: What Your Numbers Mean
pH measures how acidic or alkaline your water is on a scale of 0 to 14. A pH of 7.0 is neutral. Below 7.0 is acidic; above 7.0 is alkaline. Most well water in the eastern U.S. falls between 5.5 and 7.5.
The EPA recommends drinking water pH between 6.5 and 8.5. The real concern with low pH isn't drinking it; it's what acidic water does to your plumbing. Acidic water corrodes copper pipes (causing pinhole leaks and blue-green stains), eats through fixtures and faucets, and damages water heaters.
pH Ranges and What They Mean
What Raises pH in Well Water?
The Clack 2.5 Cubic Foot Non-Backwashing Acid Neutralizer uses calcite (calcium carbonate) to neutralize acidic water. Water flows through the calcite bed and exits at a neutral pH. It handles pH levels from 5.5 to 6.9 with standard calcite. For pH below 5.5, a calcite/FloMag blend is used. For the full guide on sizing and types, see our Complete Acid Neutralizer Guide.
Important: An acid neutralizer adds calcium to the water, which increases hardness by approximately 4-6 gpg. If your water is already moderately hard, you may need a water softener after the acid neutralizer.
Manganese (Mn): What Your Numbers Mean
Manganese is measured in mg/L (ppm) and behaves similarly to iron but stains a blackish-gray color instead of orange. It appears on toilets, showers, laundry, and sinks. Manganese often occurs alongside iron in well water.
The EPA's secondary standard for manganese is 0.05 mg/L. The health-based advisory level is 0.3 mg/L for lifetime exposure and 1.0 mg/L for short-term exposure (10 days). At high levels, manganese can affect the nervous system, particularly in infants and children.
Manganese Ranges and What They Mean
What Removes Manganese from Well Water?
The same Fleck 2510AIO Katalox Light system that removes iron also removes up to 15 ppm of manganese. One system handles both. Read more in our Iron and Manganese in Well Water guide.
Sulfur / Hydrogen Sulfide (H₂S): What Your Numbers Mean
Hydrogen sulfide (H₂S) is the gas that creates the "rotten egg" smell in well water. It's measured in mg/L (ppm), but here's the catch: H₂S is a dissolved gas that escapes water quickly. By the time a lab tests your sample, the level has often decreased. If you smell rotten eggs when running water but your lab report shows zero, it's likely still present.
There is no EPA maximum contaminant level for hydrogen sulfide. The recommended goal is zero. Any detectable level causes odor problems.
Sulfur/H₂S Ranges and What They Mean
What Removes Sulfur from Well Water?
The Fleck 2510AIO with Katalox Light removes up to 10 ppm of hydrogen sulfide along with iron and manganese. It oxidizes the dissolved H₂S gas and filters it out without chemicals. Read our full Best Sulfur Filter for Well Water guide.
Tip: If your report shows 0 ppm sulfur but you still smell rotten eggs, the H₂S may have escaped the sample before the lab tested it. Trust your nose. If you smell it, it's there. Call Aidan at 800-460-5810 and describe what you're experiencing.
Coliform Bacteria: What "Positive" Means
Bacteria results on a water test are reported as "present" or "absent" (sometimes "positive" or "negative"). This is not a number; it's a pass/fail test. Some labs also test for E. coli specifically, which indicates fecal contamination.
The EPA maximum contaminant level for total coliform is zero. Any detection of coliform bacteria means your water supply has been contaminated, usually from bugs, rodents, or surface water entering the well casing.
Bacteria Results and What They Mean
How Is Bacteria Treated in Well Water?
The Viqua VH410 UV System disinfects water as it passes through, killing 99.99% of bacteria without chemicals. The UV light destroys the DNA of bacteria and viruses so they can't reproduce. It's installed as the last system in the treatment sequence (after all other filters). Read our Iron Bacteria in Well Water guide for more on bacterial contamination.
First step if bacteria is positive: Have your well cap inspected. A proper sanitary well cap creates an airtight seal. If it's loose, cracked, or missing the rubber gasket, that's likely how contamination entered. Fix the cap, then shock-chlorinate the well, then retest. If bacteria persists after fixing the cap, install UV treatment as a permanent solution.
Total Dissolved Solids (TDS): What Your Numbers Mean
TDS measures the total amount of dissolved minerals, salts, and other substances in your water, reported in mg/L (ppm). It's a catch-all measurement that includes everything dissolved in the water: calcium, magnesium, sodium, potassium, bicarbonates, chlorides, sulfates, and more.
The EPA's secondary standard for TDS is 500 mg/L. This is an aesthetic guideline, not a health limit. High TDS can affect taste (salty, bitter, or mineral flavor) and may indicate other water quality issues.
TDS Ranges and What They Mean
How Do You Treat High TDS?
The only effective whole-water TDS treatment is reverse osmosis (RO). The Pure-75 Reverse Osmosis System reduces TDS and other contaminants by up to 75% or more. RO systems are typically installed under the kitchen sink for drinking and cooking water, not whole-house. For most well water situations, treating specific contaminants (iron, hardness, pH) with targeted systems is more practical than trying to reduce total TDS.
Context matters with TDS: A TDS reading of 400 ppm doesn't tell you what's in the water. It could be harmless calcium and magnesium, or it could include nitrates, chlorides, or other concerning minerals. Look at the individual contaminant results on your test to understand what's contributing to the TDS number.
Example Water Test Report Walkthrough
Here's an example of what a typical well water test report looks like and how to interpret it. This represents a common scenario we see from homeowners in the Mid-Atlantic region.
Sample Well Water Test Results
| Parameter | Your Result | Unit | EPA Standard | Assessment |
|---|---|---|---|---|
| pH | 6.2 | pH units | 6.5 - 8.5 | ⚠ Mildly acidic |
| Iron (Fe) | 4.5 | mg/L | 0.3 mg/L (SMCL) | ⚠ Heavy iron |
| Manganese (Mn) | 0.25 | mg/L | 0.05 mg/L (SMCL) | ⚠ Elevated |
| Hardness | 8 | gpg | None (aesthetic) | ⚠ Hard water |
| Sulfur (H₂S) | 0 | mg/L | None | ✓ OK |
| Total Coliform | Absent | P/A | 0 (MCL) | ✓ OK |
| TDS | 310 | mg/L | 500 mg/L (SMCL) | ✓ OK |
What This Homeowner Needs
This report shows three issues that need treatment, installed in this order:
- Acid Neutralizer (pH 6.2 → raise to 7.0+). Install first because iron filtration and softening work better at neutral pH. The acid neutralizer will add approximately 4-6 gpg of hardness.
- Iron Filter (4.5 ppm iron + 0.25 ppm manganese). The Katalox Light system handles both iron and manganese in a single unit.
- Water Softener (8 gpg hardness, plus the 4-6 gpg added by the neutralizer = 12-14 gpg total). Install last to remove all hardness including what the acid neutralizer adds.
No sulfur treatment, bacteria treatment, or TDS treatment needed. Three systems solve all the issues. This is one of the most common treatment configurations we recommend. Call Aidan at 800-460-5810 for sizing based on your home's water usage and number of bathrooms.
Common Well Water Test Numbers Explained
Here are some of the specific numbers homeowners ask about most often. If you Googled a number from your water test, this section is for you.
| Test Result | What It Means | Treatment Needed? |
|---|---|---|
| Iron 0.5 ppm | Light iron. Staining starting on white surfaces. | Iron filter |
| Iron 3 ppm | Moderate to heavy iron. Persistent orange staining. | Iron filter |
| Iron 6 ppm | Heavy iron. Discolored water, heavy staining everywhere. | Iron filter |
| Iron 10 ppm | Severe iron. Rapid staining, clogged fixtures. | Heavy-duty iron filter |
| Iron 20 ppm | Very severe. Requires high-capacity system. | 3.5 cu ft iron filter |
| Hardness 5 gpg | Moderately hard. Some spotting, manageable. | Softener optional |
| Hardness 10 gpg | Hard water. Scale buildup on fixtures and appliances. | Water softener |
| Hardness 20 gpg | Very hard. Heavy scale, soap won't lather well. | Water softener |
| pH 5.5 | Very acidic. Active copper corrosion, blue-green stains. | Acid neutralizer |
| pH 6.0 | Acidic. Corrosion occurring, especially with copper pipes. | Acid neutralizer |
| pH 6.5 | Slightly acidic. Monitor; treat if you have copper plumbing. | Neutralizer recommended |
| pH 7.0 | Neutral. Ideal. No pH treatment needed. | None |
| Manganese 0.1 ppm | Above SMCL. Black/gray staining starting. | Iron/manganese filter |
| Manganese 0.3 ppm | EPA health advisory level. Staining plus health concern. | Iron/manganese filter |
| Manganese 0.5 ppm | High manganese. Significant staining. | Iron/manganese filter |
| TDS 350 ppm | Normal for well water. No treatment needed. | None |
| TDS 600 ppm | Slightly elevated. Mineral taste possible. | RO optional |
| Bacteria: Present | Contamination detected. Do not ignore. | UV system |
Treatment Order: What Gets Installed First
If your water test shows multiple issues (which is common), the treatment systems need to be installed in the correct sequence. Water flows through each system in order, and each system prepares the water for the next one.
Correct treatment sequence (water flows left to right):
(if pH < 7)
(if iron, Mn, or H₂S)
(if taste/odor)
(if hard water)
(if bacteria)
Not every home needs all six. Most need 2-3 systems based on their water test results.
Why order matters:
- Acid neutralizer before iron filter: Iron filters perform best at pH 6.5+. If your pH is low, the neutralizer raises it first.
- Iron filter before softener: Iron clogs and damages softener resin. Remove it before the water reaches the softener.
- Softener before UV: UV light needs clear water to be effective. Turbidity from minerals reduces UV penetration.
- UV light last: UV should be the final point of treatment so nothing downstream can re-introduce contamination.
For the complete explanation, see our Complete Guide to Well Water Filtration Systems.
Frequently Asked Questions
What is the most important number on a well water test?
Start with pH. It affects how every other treatment system performs and determines whether your plumbing is being corroded. After pH, look at iron (the most common well water contaminant) and bacteria (the only parameter with a direct health risk at typical levels). Hardness and manganese are important for protecting your home, but pH, iron, and bacteria are the three that need attention first.
My water test shows 0.3 ppm iron. Do I really need a filter?
0.3 ppm is the EPA's secondary maximum contaminant level, the threshold where staining begins. At this level, you'll likely notice faint orange marks on white surfaces. Whether you need a filter depends on your tolerance. Some homeowners treat at 0.3 ppm to prevent staining entirely. Others wait until it reaches 1+ ppm. If you're seeing stains, it's time to treat.
My lab report uses mg/L but the article says ppm. Are they the same?
Yes. 1 mg/L = 1 ppm for all practical water testing purposes. These units are interchangeable. The only exception is hardness, which labs sometimes report in grains per gallon (gpg). To convert mg/L hardness to gpg, divide by 17.1.
How often should I test my well water?
The EPA recommends testing private well water at least once per year for bacteria and nitrates. Test more often if you notice changes in taste, odor, or appearance, or if there's been flooding, construction, or agricultural activity near your well. If you've installed treatment systems, test annually to confirm they're still working properly.
Can I use a home test kit or do I need a lab test?
Home test kits from Lowe's or Home Depot are useful for quick checks of pH, hardness, and iron. For a complete, accurate analysis, a certified lab test is better. Lab tests measure exact concentrations and test for things home kits miss (like manganese and bacteria speciation). A home kit helps you understand the basics; a lab test gives you the full picture you need for treatment decisions.
My pH is 6.0 but my iron is also 5 ppm. Which do I fix first?
Fix the pH first with an acid neutralizer. Iron filters work best when pH is 6.5 or above. At pH 6.0, dissolved iron is harder to oxidize and filter out. The treatment sequence would be: acid neutralizer → iron filter → water softener (since the neutralizer adds hardness).
Do I need a water softener if my hardness is 5 gpg?
5 gpg is moderately hard. Most appliance manufacturers recommend softening at 7 gpg and above. At 5 gpg, you may notice some water spots and slight soap residue, but it's manageable. If you also have an acid neutralizer (which adds 4-6 gpg), your total hardness becomes 9-11 gpg, and a softener becomes recommended.
What does "SMCL" mean on my water test report?
SMCL stands for Secondary Maximum Contaminant Level. These are EPA guidelines for contaminants that affect the taste, odor, or appearance of water, not health. Iron (0.3 mg/L), manganese (0.05 mg/L), and TDS (500 mg/L) all have SMCLs. They're not legally enforceable for private wells, but they indicate the levels where problems begin.
My bacteria test was positive. Is my water safe to drink?
No. A positive coliform bacteria test means your water supply is contaminated. Do not drink the water until the source is identified and the water is treated. Use bottled water for drinking and cooking. Have your well cap inspected, shock-chlorinate the well, and retest. If bacteria returns, install a UV disinfection system for permanent protection.
Can Aidan look at my water test for free?
Yes. Call Aidan at 800-460-5810 or text a photo of your water test results to 443-277-2204. 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. This is what we do every single day.