Silent Spring Institute

Frequently Asked Questions


How do I get my well water tested?


When selecting a laboratory for water testing, be sure to select a laboratory that is certified by the Massachusetts Department of Environmental Protection (MassDEP).  You can request price quotes from several laboratories, but it is recommended that you take into consideration other factors beyond cost, including laboratory detection limits, ability to use US EPA approved methods, and range of testing offered.

You can read more about water testing on MassDEP’s website and review the list of MassDEP-certified labs.


How often should I get my well tested?


Private well owners are generally not required to test their water quality, but MassDEP strongly urges private well owners to get their well tested as least once a year.  The Centers for Disease Control and Prevention also recommends testing if there are known problems with well water in your area, you have experienced problems near your well (flooding, land disturbances, nearby waste disposal sites, etc.), you replace or repair any part of your well system, or if you notice a change in water quality (taste, color, or odor).

The University of Rhode Island Water Quality Program has created a testing schedule that outlines what compounds to test for and how frequently you should test them.

Regular testing will allow you to monitor your well over time. Look for trends, and be aware of increasing contaminant levels.


How should I pick which contaminants to test for?


Most contaminants fall under one of two categories: primary and secondary contaminants. Primary contaminants are ones for which EPA has identified a health risk from excessive exposure and has set a maximum contaminant level (MCL) or action level (AL). Secondary contaminants are contaminants that have an aesthetic effect, such as taste, odor, and color. These contaminants are not typically regarded as a health risk.

It is also common to test for Water Quality Indicators (WQI), which include measurements that help to assess the acidity and amount of germs/bacteria in water. Examples of WQIs include total coliform, fecal coliform, and pH.

Many labs offer standard packages for private well owners. These packages include a mixture of common primary and secondary contaminants as well as WQIs. If you have young children, you should be aware of which contaminants might have a greater negative effect on them, such as lead and nitrate.


What does “Not Detected” mean?


Some of the chemicals in your report may not have been found at a level the lab could measure. In this case, you may see the words “not detected” or “ND” next to a chemical name. You may also see a “<” followed by a number. 

Your report will also show a detection limit or reporting limit. This is the lowest level that the lab can report to you. Laboratories with lower detection limits or reporting limits have more sensitive testing that can measure lower chemical levels. Being below the lab’s limit does not necessarily mean that the chemical is not present in your sample, and can mean that the chemical is present at a low level that the laboratory could not detect.


Which type of treatment should I select?


For each contaminant, we include tips on reducing exposure, including some well treatment options. Our “Water treatment” page includes information on common well water treatment systems and which compounds they are effective at removing.

If you decide to treat your water, there are several things you should keep in mind.

  • What chemicals you want to remove: Different treatment systems remove different chemicals, and it may not be necessary to lower levels of all chemicals in you water. Deciding what the goal of the treatment system is will help you select the appropriate system.
  • Whole-house or point-of-use system: A whole-house system treats all household water for drinking, cooking, showers, clothes washing, etc. Point-of-use systems are smaller and treat only the water that comes through the tap where the treatment system is installed. For example, they can be installed on a kitchen tap and used for drinking or cooking. Depending on the chemicals you are concerned about, you may not need to filter all the water in your home. A whole-house system will not eliminate chemicals associated with the plumbing inside your home because the water is filtered at the point of entry before it is distributed throughout your home.
  • Cost: Consider additional costs beyond just the treatment system itself, including installation and maintenance.
  • Effort to maintain: Think through any part replacement that may need to occur, who will do the maintenance, and any possible need to “flush” the system, which could have an impact on septic systems.


How do I learn more about specific water contaminants, water testing, and home water treatment?


More information on specific water contaminants:

More information about water testing:

More information about home water treatment:


What other chemicals might be in my water that aren’t being tested for?


Some labs offer additional testing for emerging contaminants that aren’t regulated in drinking water, like pharmaceuticals and consumer product chemicals. Many scientists are studying the levels of these contaminants in drinking water and their effects on human health and the environment. Pharmaceuticals and consumer product chemicals can make their way into groundwater, surface water, and drinking water wells from septic systems, sewage treatment plants, and landfills. Silent Spring Institute researchers have continued to study these chemicals in water, particularly on Cape Cod, and the effects they may have on our health. To learn about Silent Spring Institute’s research on emerging contaminants in private wells, visit: