How to Shock Chlorinate a Well
When
Penn State Extension lists: after building a new well, after well work or a new pump, and after a positive coliform test.
How much bleach
UGA Extension: 3 pints of household bleach per 100 gallons of water in the well, plus 3 pints for plumbing. Use our calculator.
Steps
- Bypass treatment equipment that chlorine can damage.
- Pour diluted bleach into the well and recirculate with a hose until you smell chlorine.
- Run each tap until it smells of chlorine, then let it sit, often 12–24 hours.
- Flush outdoors, away from septic systems and streams, until the smell is gone.
Retest
Penn State Extension says to retest about 10–14 days later, and again 2–3 months later. If bacteria return, continuous disinfection may be needed.
Sources
- Penn State Extension: Shock chlorination of wells and springs
- UGA Extension: Disinfecting your well water, shock chlorination
- CDC: How to disinfect wells after an emergency
Questions
Does shock chlorination fix bacteria permanently?
Only if the cause was one-time. Penn State found it was most successful with low coliform counts and no E. coli.
Free well water safety checklist
15 family-friendly steps based on CDC and EPA guidance. Print it, keep it on the fridge, and know when to call a certified lab.
More guides
- Flood Protection for Well Owners: Before, During and After a FloodRaise and seal the wellhead, know your pump shutoff, then disinfect and test with a certified lab after any flood.
- PFAS “Forever Chemicals” in Private Wells: Why You Should TestFederal PFAS rules protect public water systems — not private wells. Here’s what “forever chemicals” mean for well owners and how to get tested.
- Nitrates in Well Water and Blue Baby Syndrome: Who Must TestNitrate in well water can cause blue baby syndrome in infants. Learn who is at risk, when to test, and how to find a certified lab.
- Arsenic in Private Well Water: The Invisible Risk UndergroundArsenic in groundwater is often naturally occurring and invisible. USGS research shows millions of private-well users may be above the EPA drinking-water standard.