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If your well water has tested positive for coliform bacteria, you may want to disinfect (chlorinate) your well.  Please read carefully and follow these instructions!

Equipment: 

• One cup granular chlorine or 1 gallon regular unscented liquid bleach
• Clean hose(s) that extend from outside spigot to well
• Wrenches to remove well cap
• 5-gallon bucket
• Small cup
• Water sample bottle(s)
• Location of ON/OFF switch for well pump
• Eye and skin protection

Instructions:

• Mix 1 gallon of bleach with 4 gallons of water in a bucket. (Liquid bleach should not be used with a steel well casing - use granular chlorine.)
• Turn off the power to your well pump. Remove the well cap. Be careful if screws or bolts on the cap are rusty. Note: If the well cap has one large bolt in the center of the cap, have a licensed well contractor disinfect your well. If your well cap is buried or if you have a shallow well installation, your well does not meet current well construction requirements and may not be able to be disinfected. If you have an unsafe sample from this type of well, contact Planning & Environment at (734) 222-3800.
• Pour the chlorine/bleach mixture into the well between the casing and the cross bar or “T” bar. DO NOT pour the mixture into the 1” center hole. (Newer wells usually have markings next to the correct hole showing you where to pour the solution.) Try not to get the solution on the wire connections inside the well, as they could corrode.
• Connect a hose to an outside spigot and extend it into the well 4 feet.
• Turn on the power to the well pump. Turn on the spigot connected to the hose in the well. Let the hose run for 20 minutes, then turn off the spigot.
• Turn off the power to the well pump. Remove the hose from the well, and put the well cap back on the well. Turn on the power to the well pump.
• Now it’s time to distribute the disinfectant to the pipes. Turn on each indoor and outdoor water faucet, and let cold water run until a you can smell the bleach. Run the shower, clothes washer, dishwasher, outside hydrants, and plumbing fixtures in other buildings. Flush each toilet a couple of times. Once you can smell the bleach, turn off all faucets. Note: Some water softeners should not be chlorinated. Contact your water softening company before disinfection to see if you should bypass the softener.
• Let the solution to stay in the system overnight (at least eight hours). During this time you should not drink, bathe, wash clothes, or cook with the water, but you can flush the toilet.
• The next day, you need to remove the disinfectant from the system. Connect a hose to an outside spigot, turn on the water, and let the water run onto the ground for 20-30 minutes. Try to keep the water away from your drainfield and any plants or trees. Turn off the spigot and then run each indoor and outdoor faucet and appliance for 2-3 minutes to remove the solution that was in the pipes.
• You can now take the water sample!

Disclaimer:

This procedure is intended to be used for chlorinating 5” PVC wells with submersible well pumps. If your well has a jet pump (either shallow or deep), or if your casing is 4” steel or smaller, we advise that you consult with a licensed well driller prior to chlorination. These instructions are provided as public information based on conditions found in Washtenaw County. There is no implied guarantee and the procedure may have to be repeated. Washtenaw County accepts no responsibility for the outcome, or for any damage incurred.

For more information, please contact:

• Your Area Sanitarian (based on your Township)
• Department of Planning & Environment - (734) 222-3800