How do you chlorinate a well?
Last updated Reviewed by Sean Mihelich, founder of Save My Well
Chlorinating a well is the traditional treatment: figure the gallons of standing water from the well's depth, static water level, and casing diameter, dose plain unscented bleach or potable-grade calcium hypochlorite to 50 to 200 ppm per extension guidance, pour it down the casing, recirculate with a hose, pull it to every tap, hold 12 to 24 hours, then flush outside until a residual test reads zero and retest for bacteria in one to two weeks.
The words chlorinate, treat, sanitize, and disinfect all describe this same job. The part people skip is the first step: without the gallons, the dose is a guess, and a guess is how a well ends up still positive or a house ends up smelling like a pool for a week.
The honest limitation of chlorine is chemistry: it loses most of its strength above a pH of about 7.5, burns itself up on iron, and mostly scorches the surface of biofilm. Chlorine dioxide follows the same steps at 20 ppm and holds up where chlorine quits, which is why our kit doses it instead.
Sources
Ohio State University Extension, Shock Chlorination of Wells (AEX-318), 2019
Minnesota Department of Health, Well Disinfection, 2024
Penn State Extension, Shock Chlorination of Wells and Springs, 2025
U.S. EPA, Alternative Disinfectants and Oxidants Guidance Manual (EPA 815-R-99-014), 1999
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