How do you disinfect a well?
Last updated Reviewed by Sean Mihelich, founder of Save My Well
Disinfecting a well means dosing its full water system with a disinfectant strong enough to kill the bacteria living there, holding it for the contact time, then flushing it out and proving the result with tests. The traditional route is chlorine treatment at 50 to 200 ppm per extension guidance; the newer route is chlorine dioxide at 20 ppm per its manufacturer's published range. Both follow the same steps, and both start from one number: how many gallons your well holds.
The steps in brief, for our chlorine dioxide kit as its label directs: bypass softeners and filters, activate one pouch at a time in the kit's lidded mixing pail of water to make a 500 ppm stock, pour the amount sized to your gallons into the well, circulate it with the well pump, run it to every tap, let it stand overnight, about 12 hours, with no water use, then flush outside and through every outlet. A bleach treatment follows its own extension guidance.
The words sanitize, disinfect, chlorinate, and treat all describe this same job. What changes the outcome is not the word but the dose being sized to your actual well and the result being verified with a bacteria retest.
Sources
Penn State Extension, Shock Chlorination of Wells and Springs, 2025
Ohio State University Extension, Shock Chlorination of Wells (AEX-318), 2019
Minnesota Department of Health, Well Disinfection, 2024
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