The National Ground Water Association recommends household well owners test their water at least annually for bacteria, nitrate, and any contaminants of local concern.
More frequent testing should be considered if:
•There is a change in the taste, odor, or appearance of the well water, or if a problem occurs such as a broken well cap, inundation by floodwaters, or a new contamination source
•The well has a history of bacterial contamination
•The septic system has recently malfunctioned
•Family members or house guests have recurrent incidents of gastrointestinal illness
•An infant is living in the home
•One wishes to monitor the efficiency and performance of home water treatment equipment.
Well owners should check with their local health or environmental health department for recommendations regarding the type and frequency of testing specific to their location. For help in interpreting water test results -- and what might be a health risk or an aesthetic issue -- the lab that conducted the test or the county health department should be contacted.
Total coliform is the most commonly used indicator of bacterial contamination. The presence of coliform bacteria is an "indicator" of a well's possible contamination from human or animal wastes. Total coliform are a broad category of bacteria, most of which pose no threat to humans. Some come from fecal matter; others naturally occur in soils, vegetation, insects, etc. The presence of coliform bacteria in well water can be a harbinger of worsening water quality. In some cases, more specific tests for fecal contamination, such as E. coli, may be used.
Common sources of nitrate to well water are fertilizers, septic systems, animal manure, and leaking sewer lines. Nitrate also occurs naturally from the breakdown of nitrogen compounds in soils and rocks.
High levels of nitrate in well water present a health concern and can also indicate the presence of other contaminants, such as bacteria and pesticides. Drinking large amounts of water with nitrates is particularly threatening to infants (for example, when mixed in formula).
States may recommend or require testing for certain contaminants specific to the locality. Arsenic and radon are two examples of water-quality concerns that can be localized. Arsenic occurs in water that comes into contact with some types of rocks and soils. Radon is a colorless, odorless, and tasteless gas that comes from the natural radioactive breakdown of uranium in the ground. Exposure to radon can come from two sources: the air in one's home, which seeps up through the foundation, and well water. (Note: Arsenic and radon are used here as examples only, and may or may not be a problem in one's area. Well owners should check with their state or local health department.)
To find state-specific information relating to private wells, visit the water testing page located under the water quality menu tab on http://www.WellOwner.org.
Indicators of a dirty well include cloudy water, low water flow into the well, or taste or odor problems. If these problems persist, or positive bacteria results are reported from well testing, then NGWA recommends that a qualified water well system professional should inspect the well. The professional would also determine whether the well should be cleaned.
In addition to WellOwner.org, NGWA has other resources to help private well owners including a toll-free Private Well Owner Hotline at 855 420.9355 (855 H2O-WELL) and the Private Well Owner Tip Sheet -- a free monthly e-mail containing tips to help well owners take care of their well and protect water quality. One can sign up for the free tip sheet at WellOwner.org.