Water Test Results Explained: Understanding your water test report doesn’t have to be confusing. Most reports are filled with acronyms, ranges, and numbers that assume you already know what ND, TDS, PPM, hardness, pH, and metals mean.
This guide breaks down each term in simple language and links to deeper explanations so you can interpret your results with confidence. Whether you’re testing municipal water, well water, or troubleshooting a specific issue, these basics will help you understand what your numbers really mean.
1. ND (Non‑Detect)
ND stands for Non‑Detect, meaning the lab did not find the contaminant at or above its detection limit. This does not always mean the contaminant is completely absent—it simply means the level is too low for the test to measure. Detection limits vary by lab and test method, so ND is best interpreted as “below measurable levels.” ND is ideal for contaminants like lead, PFAS, and harmful bacteria.
2. TDS (Total Dissolved Solids)
TDS measures the total amount of dissolved minerals, salts, and organic matter in your water. It’s not a contaminant itself—it’s a general indicator of mineral content. Typical ranges include:
- 0–50 = Very low (common in rain-fed regions)
- 50–150 = Normal municipal water
- 150–300 = Mineral-rich
- 300+ = Hard or very mineralized
High TDS can affect taste, scale buildup, and appliance lifespan, while very low TDS can make water taste flat.
3. PPM (Parts Per Million)
PPM is simply a unit of measurement used throughout water testing. Many results—including TDS, hardness, nitrates, chlorine, and metals—are reported in PPM. One PPM equals one milligram per liter (mg/L). Understanding PPM helps you compare results across different contaminants and treatment guidelines.
4. Hardness (Calcium + Magnesium)
Hardness measures the concentration of calcium and magnesium minerals. These minerals cause scale buildup, cloudy glassware, and reduced soap effectiveness. The general hardness scale is:
- 0–60 mg/L = Soft
- 61–120 mg/L = Moderately hard
- 121–180 mg/L = Hard
- 180+ mg/L = Very hard
Hard water is not harmful, but it can affect plumbing, appliances, and cleaning. If your hardness is high, you may notice scale on faucets or white spots on dishes.
5. Chlorine & Chloramine
Municipal systems use chlorine or chloramine to disinfect water. Typical levels range from 0.2–4.0 PPM. Higher levels may cause taste or smell issues, especially after heavy rainfall or system maintenance. If the smell is strongest in hot water, your water heater may be amplifying the odor.
Learn more about chlorine smell
6. Metals (Lead, Copper, Iron, Manganese)
Metals can enter water from plumbing corrosion, well water geology, or municipal infrastructure. Key points include:
- Lead should always be ND.
- Copper can spike after water sits in pipes overnight.
- Iron and manganese cause staining, metallic taste, and discoloration.
If your results show elevated metals, the cause is often plumbing-related rather than the municipal supply.
7. PFAS (Forever Chemicals)
PFAS are synthetic chemicals found in many consumer products. They are measured in parts per trillion (PPT), and even low numbers matter. ND is ideal. If your test shows detectable PFAS, you may need a specialized filter such as activated carbon or reverse osmosis.
8. pH
pH measures how acidic or alkaline your water is. The normal range for drinking water is 6.5–8.5. Low pH can cause corrosion and metal leaching, while high pH can affect taste and soap effectiveness. pH does not indicate contamination—it simply describes water chemistry.
9. Why Water Test Results Vary
It’s normal for water test results to change slightly over time. Variations can come from temperature changes, water sitting in pipes, seasonal shifts, plumbing work, or municipal treatment adjustments. If your results fluctuate, look for patterns such as time of day or whether the water has been stagnant.
Learn more about varying results
10. How to Read a CCR (Consumer Confidence Report)
Municipal water systems publish annual CCRs that list contaminants, ranges, treatment methods, and any violations. These reports can look technical, but once you understand the basic terms, they become much easier to interpret.
Water Test Results Explained FAQs
What does ND mean on a water test?
ND means the contaminant was not detected above the test’s detection limit.
What is a good TDS level?
Most municipal water falls between 50–150 PPM. Very low TDS is common in rain-fed regions.
Why do my water test results change?
Results vary due to temperature, plumbing conditions, seasonal changes, or water sitting in pipes.
What hardness level is considered “hard water”?
Anything above 121 mg/L is considered hard water.
References
- U.S. EPA – Home Drinking Water Testing
Official guidance on interpreting water test results, detection limits, and common contaminants. - State of Michigan – Understanding Drinking Water Sample Results
Explains ND, coliform testing, and how to interpret bacteriological results. - Illinois EPA – Sample Collector’s Handbook
Covers proper sampling methods, lab procedures, and how results are used to assess water safety.
