Environmental Health

Well Disinfection Procedures

Water in a recently drilled well is subject to contamination by the drilling operation and pipes that convey the water throughout the house. It is standard practice to disinfect the well to eliminate bacteria that may have been introduced into the system before the water may be used for drinking purposes.  Follow-up samples can determine whether or not the contamination of the well is an ongoing problem.

1. Mix 1 gallon of chlorine laundry bleach with approximately ten gallons of water. 
2. Remove the well cap and pour the solution into the well casing.
3. Run water at all of the water faucets until the bleach odor is noticeable. If you do not smell a bleach odor after 30 minutes, you may add more chlorine bleach, ½ gallon at a time, up to an additional gallon. Deeper wells may require more chlorine bleach.
4. Allow the solution to remain in the pipes for 6-12 hours by not running any water during this period.
5. Flush the bleach out of the system by running the water at one or two hour intervals until no odor is noticeable. This can be done a couple of times a day and may take several days. Take care not to run your well empty.

*Do not flush the water into your septic system. It is preferable to use an outside faucet or run a hose to discharge onto the ground. 

Once the chlorine has been completely removed from the system, contact our Office to schedule a retest.

If follow-up tests continue to show well contamination you may choose additional steps as outlined below:

1. Chlorine tablets or granulated chlorine may be used in addition to liquid chlorine beach in the disinfection procedures. Do not use pool shock tablets. Chlorine tablets may be supplied by a well driller, following manufactures instructions on how much tablets to use.
2. Once you have added chlorine to the system, run a garden hose to the well casing and allow the water to recirculate for about 1 hour. Proceed with steps 3-5.

If the water supply does not respond to at least two chlorination attempts, you may want to consider permanent disinfection such as a UV light.