Well Water Overview

Water in nature, whether surface water or groundwater, is never 100% pure. It contains a variety of dissolved minerals and gases that are usually harmless and give the water most of its taste. Some natural minerals, like iron, magnesium, or calcium can make well water aesthetically objectionable, but usually are not harmful. Water can sometimes be contaminated with things like bacteria, viruses, or chemicals that can harm our health. Contaminated water can often look, smell, and taste fine, so there is no substitute for periodic testing of well water. Proper well construction, disinfection, system maintenance, and regular water testing all help to assure safe drinking water. 

Drinking water should be free of disease-causing organisms and should not contain harmful levels of chemicals. Two standard tests — for coliform bacteria and nitrate — should be performed regularly on every well. Testing for other contaminants may also be advisable. 

A water test tells you only about the water quality at the time the sample was taken. Groundwater pumped from some wells, shallow or old wells, may vary in quality during the year, especially after heavy rainfall or melting of snow. More frequent testing of old wells or wells less than 50 feet deep is may be required. At a minimum, private wells should be tested once a year.  Whenever a well is opened, test the water afterward for coliform bacteria. Anytime that you notice a change in the quality of the water, test the well for coliform bacteria and nitrate. Before collecting a water sample for testing, contact ABE Laboratories for bottles and instructions. 

The Total Coliform Bacteria Test

 Waterborne diseases can be spread by drinking water that has been contaminated with fecal wastes from humans or animals. Examples of these diseases include salmonellosis, dysentery, and hepatitis. It may take only a small number of disease organisms to make someone sick. The symptoms of these diseases often include diarrhea, nausea, vomiting, and sometimes fever. It is not unusual for people to mistake a case of water-related disease for “food poisoning” or a “24-hour flu bug.” Remember, contaminated water can often look, smell, and taste fine. 

It is not practical to test water for every possible disease-causing organism. Instead, water is usually tested for one particular group of bacteria known as the total coliform group. These organisms serve as indicator bacteria — they indicate how sanitary your water system is.   Coliform bacteria can be found everywhere on the land surface but are usually not found more than a few feet below the soil surface. Coliform bacteria are also found in the intestinal tract (and fecal wastes) of all warm-blooded animals.  Most coliform bacteria do not usually cause disease, but if they show up in a water test, they indicate that surface contamination has somehow entered the water and disease-causing organisms may also be present. Remember that waterborne infectious disease is caused by fecal contamination, which is usually found only on the ground surface (in the case of animal waste) or near the surface (in the case of contamination from sewers or septic systems). 


Coliform bacteria are also good indicators of the sanitary quality of your water because they are killed in the same way that most disease-causing organisms are killed. With few exceptions, if a well is disinfected with a solution of chlorine and the coliform bacteria disappear, disease-causing organisms in the well have also been killed. 


Disinfection with a chlorine solution will usually eliminate bacteria and viruses if they entered the well during construction or repair of the well — when a new pump is installed, for example.  Disinfection or treatment will not provide a permanent solution if the contamination is caused by faulty well construction, a failing septic system, surface water contamination, or some other ongoing problem. In that case, it will be necessary to repair the well, construct a new well, or remove the source of contamination.  In order to stay on top of the situation, the U.S. Environmental Protection Agency (EPA) recommends periodic surveillance for coliform bacteria every six months.

The Nitrate/Nitrites Test

The presence of elevated levels of Nitrate and/or Nitrite, chemicals containing nitrogen and oxygen, in your water can result in serious medical problems with pregnant women and children under the age of six months.

Both compounds move easily through the soil to the groundwater. In some cases, Nitrate and Nitrite occur naturally in groundwater that is near the surface, but the levels are usually low.  Elevated levels of Nitrate/Nitrite in groundwater usually indicate contamination from fertilizers, animal wastes, or subsurface sewage treatment systems. In some wells, particularly drive-point wells or other shallow wells, Nitrate/Nitrite may only be present during the spring, or after a heavy rainfall when rapid infiltration of surface water occurs. Because these contaminants can move rapidly down through the soil into the groundwater, their presence may provide an early warning of possible problems and can sometimes indicate the presence of other contaminants. 


Boiling the water will not remove the Nitrate or Nitrite. It will instead increase the concentration in your water, due to evaporation of some of the water. Also, it is not recommended to rely on a home water treatment device to remove Nitrate/Nitrite from water fed to infants, because there is usually no way to immediately tell if a treatment device has malfunctioned. For infant feeding, use water from a source that is known to have low Nitrate/Nitrites. 


The EPA recommends periodic surveillance for nitrate every six months.

Other Tests

Even if testing detects no nitrate or coliform bacteria, well water could contain other contaminants such as arsenic, lead, pesticides, or “volatile organic chemicals” (from petroleum products or solvents). There is no single test that covers all possible contaminants.  

Hardness is caused primarily by calcium and magnesium ions, but also by iron and manganese ions present in the water. The higher the concentration of these minerals, the greater amount of soap that is required to produce suds. The soap that is combined with the minerals leaves an insoluble scum, which causes laundry and staining problems. Testing for hardness can help you develop an effective water treatment program. Hardness in water does not cause detrimental health effects. 


Iron is naturally present in some groundwater.   It is typically not a health concern, but concentrations above certain levels will discolor your water and cause an objectionable metallic taste. It can also cause reddish brown stains on plumbing fixtures and clothes during laundering, encrust well screens, and clog pipes.  


Lead is usually not found in groundwater, but water can dissolve lead from old lead pipes, lead-soldered copper pipes, or brass plumbing components when the water stands in the plumbing system for more than a few hours at a time. Infants, children, and pregnant women are especially vulnerable to the potential health effects of lead. Too much lead can damage the nervous system, red blood cells, and kidneys. 

pH is a measure of the concentration of hydrogen ions in a diluted solution. It can range from 0 to 14, with 7 denoting a neutral value. Acidic water has a pH below 7; alkaline water has a pH above 7. The health effects of pH on drinking water depend upon where the pH falls within its range. The U.S. Environmental Protection Agency, which classifies pH as a secondary drinking water standard, recommends a pH between 6.5 and 8.5 for drinking water.  Neutral and acidic waters combined with low calcium and alkalinity levels tend to make the water corrosive.

Total Dissolved Solids (TDS) is a measure of the combined content of all inorganic and organic substances contained in a water sample which are small enough to survive filtration through a filter pore size of two-micrometers.  Primary sources for TDS in receiving waters are agricultural and residential runoff, leaching of soil contamination and point source water pollution discharge from industrial or sewage treatment plants. Elevated TDS can lead to scale formation, hardness and a salty taste.