Understand Your Results
More than 100 drinking water contaminants are regularly analyzed by the North Carolina State Laboratory of Public Health. Deciding for which contaminants to test and receiving the results can be overwhelming. Numerous factors can influence which contaminants might be of concern in your area, including the geology, local land use, and hazardous spills near your well.It can also be challenging to interpret all of the numbers, abbreviations, and acronyms that appear on the results forms. This page contains samples of the well-testing request and results forms used by the NC State Laboratory of Public Health, a sample analysis report used by the NC Division of Public Health, and an explanation of the features found on each of these forms.
What contaminants should I test for?
Prior to submitting a well water sample for analysis, private well owners must identify the contaminants for which they would like to test. This information should be recorded on a submission form that accompanies the well water sample.
View the report for your county or contact the environmental section of your local health department for more information about which contaminants are recommended for testing in your area.
The NC Division of Public Health recommends testing your well water every year for coliform bacteria, every two years for heavy metals, nitrates, nitrites, lead, copper, and volatile organic compounds, and every 5 years for pesticides.
The US Environmental Protection Agency (US EPA) set legal limits on 15 inorganic contaminants in drinking water and secondary guidelines for an additional 15 contaminants. Secondary guidelines are based upon the likelihood of a contaminant to cause aesthetic changes to the quality of your water by affecting the appearance, odor, or taste.
The US EPA defines inorganic contaminants as mineral-based compounds such as metals, nitrates, and asbestos. Inorganic contaminants are naturally-occurring in some water, but can also enter water through agriculture, chemical manufacturing, and other human activities.
There are legal limits on 56 organic contaminants in drinking water.
Organic contaminants are carbon-based chemicals, such as solvents, petroleum products, and pesticides. These contaminants can get into water through runoff from croplands, leaking from underground storage tanks and vehicles, or discharges from factories.
Receiving well-testing results
After sending a well water sample to a certified laboratory for analysis, well owners will receive a form containing the results of the analysis. The form will contain a list of the contaminants for which the water was tested and the amount (if any) of contaminant(s) detected in the sample. Below is a sample well-testing form and an explanation of common headings on the form.
Headings that appear on the results form
Analyte: The substance or contaminant that was tested in your well water sample.
Result: The concentration of the contaminant that was tested in your well. In some cases, the amount of the contaminant in the water sample is so small that the analytical devices in the laboratory cannot provide a numerical result. These values are referred to as “below detect” or “trace”. If these items appear on your well-testing results, the contaminant is at a very low concentration or even non-existent in your well water sample.
RL (Reporting Limit): The reporting limit is comparable to the Method Detection Limit (MDL) reported by the US EPA. The reporting limit is the minimum concentration of a substance that can be routinely reported using current laboratory methods.
Unit: The unit is the standard reporting measure for that contaminant. Some contaminants are reported in mg/L (milligrams per Liter). Others are reported as µg/L (micrograms per Liter). A microgram is 1000 times smaller than a milligram. It is important to read which units the values are reported in on your results form and online materials. All units reported on this website are micrograms per Liter (µg/L).
Mg/L can be referred to as Parts Per Million (PPM). Another way of referring to µg/L is Parts Per Billion (PPB).
Qualifiers: Qualifiers are important notes about your well water sample written by the sampling laboratory. Occasionally the qualifier will indicate that the sample was not able to be analyzed, or that there was some other contaminant of concern. The qualifiers may also mean that you should re-submit a water sample or contact the county Health Department. Qualifiers are indicated in the right column of the results form and are defined on the last page of all well-testing results.
View recent well-testing results
Select a category of contaminant from the list below to view recent well-testing results recorded by the North Carolina State Laboratory of Public Health.
What is the well water analysis report?
The well water analysis report accompanies all well-testing results sent to well owners in North Carolina. The North Carolina Division of Public Health (NC DPH) evaluates all well-testing results processed by the NC State Laboratory of Public Healthy and determines whether the water sample meets state and federal drinking water standards.
If your well water is contaminated, toxicologists in the NC DPH will review the results to determine if your water can continue to be used for drinking or other household tasks such as bathing, showering, and washing clothes and dishes.
This project was funded by an ARRA supplement from the National Institute of Environmental Health Sciences (#P42ES005948) 2009-2011.