Rainwater that percolates into the ground, collects and moves through soil and rock layers. Wells provide homes and communities access to this water. Private residential wells are not normally tested by health departments. Homeowners must test their own well water to ensure it is safe to use. While wells can be a safe water source, groundwater also may be contaminated by potentially harmful bacteria, naturally occurring minerals, or chemicals from agricultural or industrial sources.
Well water should be tested for the presence of coliform bacteria, with emphasis on E. coli. Coliform bacteria are found in the soil and in groundwater directly affected by surface water. One group of coliform bacteria indicates the presence of fecal material in the well water. E. coli, a prominent member of this group, can cause illness and is used as an indicator that the water may contain other illness-causing organisms.
Nitrates come from fertilizer and can seep into the ground and get into the water supply. Also, oxygenated water, combined with decaying plant mater, can create nitrates. Nitrates can harm infants and pregnant women. Well owners should test their wells for nitrates at least once and should consider testing the well regularly if the home is close to agricultural operations.
Homeowners who live near agricultural areas should learn what pesticides the local farmers use on their farms, and test their well water to determine whether the groundwater is contaminated by pesticides. One of the most common agricultural pesticides is atrazine, a herbicide. This pesticide’s presence or absence in the well water may be used as an indicator of whether pesticide contamination in general is apt to be a problem.
Copper and Iron
When first drawing water from the water table while constructing the well, the homeowner should test for the presence of iron and copper. Iron can cause nervous system and kidney problems, while copper can cause an upset stomach, diarrhea and headaches.
Fuel and Solvents
All homes can potentially have gasoline, fuel oil, paint thinners and other solvents in their ground water. However, wells near landfills, industrial sites, auto-repair shops or dry cleaners are those most likely to be contaminated by such substances, many of which can cause cancer.
While not common, other substances that can be present in ground water from natural sources or through human activity include arsenic, radium, radon and boron. Well owners should test at least once for these substances.
Homeowners may want to test their water for iron and sulfur bacteria. While these bacteria do not cause health problems, they can affect the taste of the well water and give it a rotten egg smell or make it feel slimy.