Silent Spring Institute

Interpreting Your Results

To use this tool to create your personalized report, you will need to find a few pieces of information from your most recent water quality testing report. See below for instructions.

Input Your Data

Your results are anonymous. Read more about how we protect your privacy here.



What to look for in your water quality testing report

1. Compound

Water quality laboratories test for a range of contaminants. Currently our tool can create a report for 15 contaminants commonly measured in private wells:

  • Aluminum
  • Arsenic
  • Chloride
  • Copper
  • Fluoride
  • Iron
  • Lead
  • Manganese
  • MTBE
  • Nickel
  • Nitrate (or Nitrate Nitrogen)
  • Nitrite (or Nitrite Nitrogen)
  • Radon
  • Sodium
  • TCE
  • Uranium

Select the name of the contaminant from the drop down menu. Click “Add Another” to enter data for multiple contaminants.


2. Value

If a contaminant was detected in your water sample, your report will contain a number that tells you the contaminant level. Type the number into this box. On your report, this information is likely called “Result.”

If a contaminant is not detected in your water sample, this information may be reported in several ways.

  • “<” followed by a number. (e.g. <3) The “<” tells you the level in your water sample was less than a certain value, and that value is typically the lowest level that the laboratory can measure. Enter both the “<” and the number that follows. For instance, just type in “<1” if that is how your result is reported.

  • ND, which stands for not detected. If your result is ND, type that into the “Value” box. You will then be asked to fill in the reporting limit, which is the lowest level that the laboratory can measure. This may be labeled in several ways on your report:
    • RL, or reporting limit
    • MRL, or minimum reportable level
    • DL, or detection limit


3. Unit

Contaminant concentrations can be measured using different units of concentration, in the same way that length can be measured in inches, feet, or centimeters. For each Value or Reporting Limit, select the appropriate unit from the drop down menu.


Other information in your report

Another useful piece of information reported by water testing laboratories is the US EPA’s drinking water standard for each contaminant. These may be labeled in one of several ways on your report:

  • MCL, or Maximum Contaminant Level. This is a health-based standard established by the US EPA.

  • SMCL, or Secondary Maximum Contaminant Level. This is a standard established by the EPA based on concerns about the appearance, taste, or odor of water.

  • Limit (not to be confused with Reporting Limits)

  • AL, or Action Level. For lead and copper, the EPA has established Action Levels as regulatory standards.



Example report from a testing laboratory


Other water quality concerns

The following are all general indicators of water quality. 


Frequently tested water quality indicators 

Massachusetts Department of Environmental Protection recommends that you test for nitrate and total coliform at least once per year. 


The U.S. EPA's standard is 10 parts per million (ppm or mg/L). Nitrate levels above 10 ppm are harmful to infants. Nitrate levels above 1 ppm show impact from human activities and may indicate the presence of other contaminants. Common sources of nitrate in private wells include septic systems or fertilizers. 


Total coliform & fecal coliform
The presence of total coliform is a sign that harmful bacteria, such as E. coli, may be present. A follow-up test for fecal coliform should be conducted. Fecal coliform are harmful bacteria found in human and animal waste. A positive test on a fecal coliform test requires immediate action. 



Common water quality indicators

Regular, but less frequent testing of your water's acidity and hardness may provide additional information to you about the quality of your water. MassDEP recommends that you test pH and hardness at least every 10 years. 

pH (acidity) 

The U.S. EPA's recommended range of pH (acidity) is 6.5 to 8.5. Water with a pH value below 6.5 can corrode pipes and release harmful lead and copper from plumbing.


Hardness is a measure related to the amount of dissolved minerals (calcium and magnesium) in water. Hard water is not harmful, but hard water can cause mineral buildup in appliances and fixtures that heat water. 


Emerging water quality concerns

Some labs offer additional testing for emerging contaminants. Scientists are learning more about these contaminants in drinking water and their effects on human health and the environment. 


PFAS (per- and polyfluoroalkyl substances) are a class of extremely persistent water contaminants found in certain firefighting foams and many consumer products. Massachusetts is in the process of finalizing a drinking water standard for the total amount of 6 PFAS chemicals. To learn more about PFAS, visit:


Pharmaceuticals and consumer products

Pharmaceuticals and consumer product chemicals can make their way into groundwater and drinking water wells from septic systems, sewage treatment plants, and landfills. To learn about Silent Spring Institute’s research on emerging water quality concerns, visit: