How much chlorine do I need to shock my well?

A general rule is 3 pints of standard household bleach (5.25% sodium hypochlorite) per 100 feet of water depth in a 6-inch diameter well. For higher-strength bleach or different well diameters, amounts vary. Target a chlorine concentration of 100-200 ppm in the well water for effective disinfection.

How long should chlorine stay in the well?

Allow the chlorinated water to remain in the well for at least 12-24 hours for effective disinfection. During this time, do not use water from the well. Longer contact times (up to 48 hours) are more effective for stubborn contamination, but most sources recommend a minimum of 12 hours.

When should I shock chlorinate my well?

Shock chlorinate your well when: a bacteria test comes back positive, after any well repairs or pump replacement, after flooding or surface water intrusion, if water develops off odors or tastes, when the well has been unused for extended periods, or annually as preventive maintenance in some cases.

Can I use pool chlorine to shock my well?

Pool chlorine (calcium hypochlorite) can be used but requires careful calculation due to its higher concentration (typically 65-70%). Household bleach is easier to measure and less likely to cause over-chlorination. Never use bleach with added fragrances, surfactants, or thickeners—plain unscented only.

Will shock chlorination harm my septic system?

Large amounts of chlorine can temporarily disrupt septic system bacteria, but a single shock chlorination typically doesn't cause lasting damage. Minimize impact by flushing chlorinated water outdoors rather than into the septic system when possible. The system usually recovers within a few days.

What if bacteria comes back after shock chlorination?

If bacteria returns shortly after chlorination, there's likely an ongoing contamination source: damaged casing, failed sanitary seal, surface water intrusion, or cross-contamination from septic. Professional investigation is needed to identify and fix the source before re-chlorinating.