E.Coli and other Coliform Bacteria can enter well water due to deteriorating well grouting or well casings that allow surface water contaminants to enter the well.  Tell tale signs of Coliform Bacteria include stomach distress after consumption of water.  Discoloration of well water after heavy rainfall can also be a sign that surface water containing bacteria is entering the well. While periodic "shocking" can provide a temporary fix, a properly designed disinfection system utilizing chlorine, ozone, and/or ultraviolet sterilization can provide the kind of continuous treatment and piece of mind most families demand.