How do I chlorinate (disinfect) my well?

The first step in the chlorination process is to know where your well is. Once found, remove the well cap.
For a typical drilled well that is 6" in diameter, 100' to 300' depth, use 1 quart of "fresh" unscented, food grade 5.25% bleach mixed with 10 gallons of water in a large "clean" container (such as a new plastic garbage can). More bleach may be needed if the well is deeper than 300 feet deep. Common household bleach contains a chlorine compound that will disinfect water.
Pour or siphon the entire solution carefully into the well, making sure that you "wash" the inner diameter of the well casing with the bleach solution.
One by one, open each cold water faucet and run the water until a strong odor of chlorine is detected. (If a slight odor is not detected, add more chlorine to 10 gallons of water and repeat the procedure.) Once chlorine odor is detected, turn off the faucet and proceed to the next faucet. If possible, work back from the furthest faucet from the well supply to the closest.
Flush the toilets.
Connect a garden hose to an outside faucet and place inside the well. Run the hose and let the water recirculate through the water system for at least 30 minutes. Replace well cap.
Let the water stand in the water system, unused, for at least 24 hours.
After 24 hours, flush the system of any remaining chlorine. Start by turning on outside faucets and letting them run until the chlorine smell dissipates. Finally, run the indoor faucets until the system is completely flushed (using a pool test kit can detect if any chlorine is present). There should be no detectable smell and the water should be clear. The water must then be retested by an approved laboratory. When collecting samples to be tested, be sure not to handle the rim of the bottle or cap with your hands.

How often should I get my well water tested?
What do I need to know to install or repair a well?
What should I do if my well water is contaminated?