Well water can cause diarrhea, an acute gastrointestinal symptom resulting from consuming water contaminated with harmful microorganisms. Unlike municipal systems, private wells are not subject to public health regulations, making the homeowner solely responsible for water safety. Groundwater, the source for most private wells, becomes polluted when surface contaminants seep into the aquifer. This contamination introduces pathogens that, when ingested, attack the digestive system and cause illness.
Pathogens Responsible for Waterborne Illness
Waterborne diarrhea agents fall into three main categories: bacteria, viruses, and parasites. These microbes enter the well, often through surface runoff or improperly functioning septic systems, carrying fecal material. Pathogenic bacteria like Escherichia coli (E. coli), Salmonella, Shigella, and Campylobacter are immediate threats that cause severe gastrointestinal distress.
Viruses such as Norovirus and Rotavirus are frequent causes of illness transmitted through contaminated drinking water. Rotavirus and E. coli are particularly common causes of diarrheal disease in children. These organisms are highly infectious and can lead to rapid onset of symptoms like vomiting and watery diarrhea.
Parasitic protozoa, including Giardia lamblia and Cryptosporidium, are a major concern. These parasites exist in a protective cyst stage, allowing them to survive for long periods and making them resistant to standard chlorine disinfection. Ingesting these cysts can lead to giardiasis or cryptosporidiosis. Symptoms often include persistent diarrhea, abdominal cramping, and nausea.
Identifying Well Contamination
Professional testing is the only reliable way to confirm well water safety, as contamination is often invisible. The Environmental Protection Agency recommends that private well owners test their water at least once every year. Annual testing should focus on Total Coliform Bacteria and E. coli, which indicate fecal contamination. The presence of coliform bacteria suggests that other harmful pathogens, including viruses and parasites, may have entered the water supply.
Annual testing should also check for nitrates, pH levels, and Total Dissolved Solids (TDS). Nitrates are concerning for infants and pregnant women, as high levels often indicate contamination from fertilizers or septic waste. Immediate testing is advised if anyone in the household experiences unexplained gastrointestinal illness.
Physical indicators can signal an acute contamination event requiring urgent action. These signs include a sudden change in the water’s taste, cloudiness, or odor, such as a sulfur or rotten-egg smell. Testing is also recommended following significant environmental events, like heavy rainfall, flooding, or snowmelt, which can push surface contaminants into the well system.
Immediate Actions and Long-Term Well Maintenance
If water contamination is suspected due to diarrhea, immediately stop drinking the well water. Safe alternatives include using commercially bottled water or properly disinfecting the existing supply. For emergency disinfection, boiling the water is the most effective method against biological pathogens.
To properly boil water, first filter it through a clean cloth or coffee filter if it appears cloudy or turbid. The water must then be brought to a rolling boil for at least one full minute to kill disease-causing bacteria, viruses, and protozoa. At altitudes above 5,000 feet, the boiling time should be extended to three minutes.
Long-Term Well Maintenance
Consistent well maintenance and proper system placement are required for long-term protection. The wellhead casing should extend above the ground surface with a secure seal to block surface water infiltration. Homeowners must also maintain a proper separation distance between the well and potential contamination sources, such as septic systems.
General guidance suggests the well should be at least 50 feet away from the septic tank and 100 feet from the drain field, though local regulations may require greater distances. Regular pumping and maintenance of the septic system are necessary to reduce the risk of wastewater seepage into the groundwater. Routine annual testing for bacteria and nitrates remains the standard practice for monitoring water safety.