Silent Spring Institute

Interpreting Your Results

This tool includes 16 chemical contaminants found in drinking water such as nitrate and lead. See the “Water Quality Indicators” tab for information on interpreting results for pH, coliform bacteria, and hardness. 

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

Once you have located the results from your water test, you can enter them here. Use the drop-down menu to select the name of a contaminant, and click “Add another” if you have results for multiple contaminants.

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