Escherichia coli, also known as E. coli, is a Gram-negative, facultatively anaerobic, rod-shaped, coliform bacterium of the genus Escherichia that is commonly found in the lower intestine of warm-blooded organisms.


Coliform bacteria are organisms that are present in the environment and in the feces of all warm-blooded animals and humans. Coliform bacteria will not likely cause illness. However, their presence in drinking water indicates that disease-causing organisms (pathogens) could be in the water system.

E. Coli

E. coli is easily identifiable at a laboratory, but figuring out which strain it is tends to be more difficult. There are close to 110 strains of E. coli, about a dozen of which are harmful. Approximately 1% of all wells on PEI test positive for E. coli, and almost 100% of E. coli problems are caused by leaky septic tanks. E. coli is usually an indicator that surface water is entering the well.


Whether you’re installing a new pump or repairing an existing one, all it takes is an insect or a blade of grass to get into the well via the pump, pipe, or electrical wire for coliform bacteria to appear. Any plumbing such as pipes, water tanks, or the like can be a temporary home for insects or spiders, and if hard-shelled bugs get into the system, it can take months of disinfecting to get a coliform count to zero.