- Runoff from woodlands, pastures, and feedlots; septic tanks and sewage plants; and animals (wild or domestic).
- Backflow from contaminated sources such as a sink-top carbon filter or bucket of water.
- Reduced pressure or suction in water lines that draws in soil water at the pipe joints.
- Through faulty sanitary seals in the well system such as when the well cap, grout around the well casing, or pitless adapter that connects an underground water distribution pipe to the well are compromised.
Many types of bacteria are native or adapted to saturated sediments and rock, and are present in significant numbers in aquifers.
Pathogens may not be present if coliforms are, but some strains of E. coli have been lethal, so their presence should be taken very seriously. Other health effects from pathogenic bacteria can include diarrhea, cramps, nausea, headaches, or other symptoms. They may pose a special health risk for infants, young children, and people with severely compromised immune systems.
People become accustomed to the natural bacteria in their water while guests may experience some discomfort or diarrhea.
Well inspections should be done by a qualified water well system professional and include visual inspect of the wellhead, well system components, and other related equipment; physical inspection of well system components; and documentation of the entire inspection.
- Disinfection, which kills the bacteria (i.e. chlorination or disinfection via chemicals, ozone, bromine)
- Filtration, which traps the bacteria
- Percolation which removes and can kill the bacteria
- Ultraviolet irradiation, which kills bacteria.
Sometimes conditions may dictate using a combination of methods to effectively deal with bacterial contamination of well water. All of these methods require proper maintenance by a qualified professional.