Understanding Your Results

DEQ recommends that you test your drinking water. As a private well owner, you are solely responsible for the quality of your drinking water. It is up to you to decide when and how to test your water.

Once you receive your lab results, the first question people usually ask is whether a detected chemical poses a health threat.  Lab results can be confusing and make it tough to understand if a detection is at a level that should be of a concern, or that could require treatment. Especially when labs may be reporting a concentration in one measurement, such as parts per billion (ppb or ug/L), and the comparison standards are listed in parts per million (ppm or mg/L), or visa-versa. If you are having trouble understanding your lab report contact the analytical lab for assistance. Ask the lab if there are any contaminants that present a health risk.

To determine if water is generally safe to drink, water test results are compared to the US EPA National Primary Drinking Water Regulations table of contaminants and the Secondary Drinking Water Standards.  The EPA Drinking Water website also provides information on potential health effects associated with various drinking water contaminants.  Arsenic and You can help you understand arsenic in drinking water and how to minimize your exposure.  In addition, there is a table below to assist with understanding your lab results.

It is a good idea to follow-up with a second test before you decide if any water treatment is needed. When considering a water treatment device, make sure its specifications match up to the substances and concentrations you wish to treat. Also, there are performance testing programs for treatment systems, such as the NSF International.


Resources

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