Disinfection is a process of killing or inactivating microorganisms to make water safe for drinking. It can also eliminate nuisance bacteria that can cause unpleasant tastes and odors. Bleaching and shock chlorination are a way to disinfect your well using chlorine bleach.

Well or water system contamination can occur when the well or plumbing is open to the environment during construction, repair, or routine maintenance. A well may also become contaminated if the well casing is deteriorated or damaged, or if the well is flooded.

Contamination problems can also be caused by improper plumbing connections between water treatment devices and wastewater piping, between the potable water plumbing and heating/cooling systems, or other cross connections.

It is recommended to test a well once a year for “coliform bacteria,” or whenever there are changes in the water’s taste, odor, or appearance. The coliform bacteria test analyzes for a number of bacterial species. Most of these are not harmful, but a few are.

Their presence indicates that surface contamination has found its way into the well, and disease organisms may also be present. The presence of E. coli or fecal coliform represents a more serious health risk, and any water use should be strictly limited to non-potable uses (not used for drinking).

The Minnesota Department of Health has provided a step-by-step procedure for disinfecting private wells and water systems using chlorine bleach (sodium hypochlorite).

If you are not comfortable with the disinfection procedure, have complex water systems, or severe contamination problems, it is recommended that you contact a licensed well contractor or pump installer to disinfect your well and water system.