Disinfection should be performed after a well is sampled and found to be either coliform positive when a presence/absence test was done, greater than the acceptable level of four colony forming units (CFUs) for total coliform, or is E. coli is present. This procedure may be carried out by homeowners on an existing well.  

Click the "Download" button to obtain the Disinfection Fact Sheet for Drinking Water Wells - Simple Procedures for Homeowners.