For more information, please contact an Area Environmental Health Specialist (based on your Township), Livingston County Environmental Health Division at (517) 546-9858.

How often should I test my well water for bacteria?

You should test your well every year for bacteria. In addition, test for bacteria if:

  • You notice a sudden change in your water’s taste, appearance, or odor.
  • The water turns cloudy after rainfall or the top of the well was flooded.
  • You suspect a contamination source (sewage system, barnyard, etc.) is within 50 feet of your well.
  • Family members are experiencing unexplained flu-like symptoms.
  • Your water supply system has been serviced or you have made changes to the system.

How do I test my well water for bacteria?

  • Obtain sample bottles from a Certified Drinking Water Laboratory.
  • When you are ready to sample, remove the aerator from the faucet, if possible. (If the aerator is difficult to remove, just leave it on). Dip the tip of the faucet into a small container of bleach for 30 seconds. Leave the bleach on the faucet for 5 minutes to kill any bacteria present.
  • After disinfection, turn on the cold water full stream and let it run for 15-20 minutes. While the water is running, remove the lid from the sample bottle. Do not touch the interior of the bottle or lid. Also, leave any pill or powder in the bottle! Turn the faucet down to a small stream and collect the sample. Fill the bottle up to the neck of the bottle (but don’t overflow!) and replace the lid.
  • Put the aerator back on the faucet.
  • Return the sample to Certified Drinking Water Laboratory.  It is best to collect the sample just before delivery to the lab. Samples should be refrigerated or chilled while stored or transported.
  • If you receive a notice that your sample is positive for bacteria, you may want to disinfect your well.

Well Disinfection (Chlorination)

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.


  • One cup granular chlorine or one 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


  1. Draw off about four gallons of water into a 5-gallon bucket.
  2. Mix one gallon of regular unscented liquid bleach with the four gallons of water.
  3. Note: Liquid bleach should not be used with a steel well casing; it can break loose accumulated corrosion and cause pump failure. Instead, use granular chlorine in a steel well casing.
  4. Turn off the power to your well pump.
  5. Remove the well cap. Be careful if set screws or bolts on your well cap are rusty.
    • Note: If the well cap has one large bolt in the center of the cap, you should not attempt to remove it. Have a licensed well contractor disinfect your well. In addition, if your well head or top is buried, or if you have a shallow well installation, your well does not meet current well construction code requirements. Chlorinating these wells is difficult and in many cases impossible. If you have an unsafe water sample and you have a well that fits this description, contact Livingston County Environmental Health.
  6. 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 will often have markings or a statement next to the correct hole, indicating where to pour the chlorinating solution.)
  7. Avoid contact of the solution with the wire connections inside the well, as they could corrode.
  8. Connect a clean hose to an outside spigot and extend it into the well approximately four feet.
  9. Turn the power supply back on to the well pump.
  10. Turn on the outside spigot that is connected to the hose in the well. Allow the hose to run in the well for approximately 20 minutes. This distributes the disinfectant throughout the well system.
  11. Turn the spigot off when done.
  12. Turn off the power supply to the well pump. Once the power is off, remove the hose from the well, and put the well cap back onto the well using the existing nuts and bolts.
  13. Turn on the power to the well pump.
  14. All work is now completed on the wellhead. Now it’s time to distribute the chlorine/bleach to the pipes. Turn on each indoor and outdoor water faucet, and allow cold water to run until a chlorine/bleach odor is detected. Don’t forget to run the shower, clothes washer, dishwasher, and any outside hydrants or plumbing fixtures in other buildings. Also, flush each toilet a couple of times. Once you detect a bleach odor, turn off all faucets.
    • Note: Some water softening units should not be chlorinated. Contact your water softening company prior to disinfection to determine if you should bypass the softening system.
  15. Allow the solution to remain in the system for a minimum of eight hours, or overnight. During this time you should not drink, bathe, wash clothes, or cook with the water, but you can use it for toilet flushing.
  16. After the solution has remained in the system for a minimum of eight hours, connect a hose to an outside spigot and allow water to run onto the ground for 20-30 minutes to remove the chlorine solution from the water system. Try to keep the water away from your drainfield and any plants or trees if possible.
  17. After 20-30 minutes, turn off the spigot and then run each indoor and outdoor water faucet for 2-3 minutes to remove the solution that was in the pipes.
  18. It is now time to collect the water sample. Remove the screen or aerator from the faucet tip.
  19. Submerge the tip of the faucet into a small container of bleach for 30 seconds. Allow the bleach to remain on the faucet tip for five minutes. (This reduces the possibility of a false-positive sample reading, as the faucet tip is a potential area of bacterial growth.)
  20. Once the faucet tip has been disinfected, turn on the cold water and allow it to run for five minutes.
  21. While the water is still running, remove the lid from the sample bottle. DO NOT touch the interior of the lid or sample bottle, and remember that the pill or powder substance in the bottle must remain inside the bottle.
  22. Fill the bottle to approximately ½ inch from the top and replace the lid.
  23. Place the screen/aerator back on the faucet.
  24. We recommend that samples be refrigerated or chilled while stored or transported. If you receive a notice that your sample is positive for coliform bacteria, or if you have any questions regarding the well disinfection procedure, please contact Livingston County Environmental Health.

Disclaimer: This procedure is intended to be used for chlorinating 5-inch PVC wells with submersible well pumps. If your well has a jet pump (either shallow or deep), or if your casing is 4-inch 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 Livingston County. There is no implied guarantee and the procedure may have to be repeated. Livingston County accepts no responsibility for the outcome, or for any damage incurred.

Last Modified December 14, 2023

Environmental Health
Livingston County Health Department Logo
Matt Bolang

Matt Bolang
Health Officer



(517) 546-9858


Monday – Friday
8:00 a.m. – 5:00 p.m.
Closed County Holidays


2300 E Grand River Ave
Suite 102
Howell, MI 48843


(517) 546-9853
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