Well Management Program
This handout provides instructions for disinfecting your water system, which includes both the well that has a submersible pump and the associated water distribution system. These instructions can be used for a single family home or businesses such as resorts and campgrounds. Disinfection can eliminate or reduce harmful bacteria, viruses, or other microorganisms that may be found in your drinking water.
You can disinfect your well by following these instructions, or you can hire a licensed well contractor. Licensed well contractors can be found at: Licensed/Registered Well and Boring Contractor Directory.
Be sure to do the following to ensure your safety and that of your family, pets, and livestock.
- Read this entire brochure before starting to disinfect your water system.
- Keep children and animals away from the well area while disinfecting.
- No one should use water from the water system until the disinfection procedures are done.
Use extreme caution when working with electricity and water. Together, water and electricity can be deadly.
- Always follow the manufacturer’s use and safety directions.
- Avoid eye and skin contact. Wear protective goggles or a face shield and rubber gloves when working with bleach.
- Do not mix bleach with other chemicals as they may form harmful gases.
- Do not leave bleach or the bleach solution unattended.
- Disinfection can create harmful gases. The area around the well must be well ventilated.
- Harmful gases can accumulate in well pits and create a lack of oxygen.
Procedure for Water System Disinfection
You will need the following to disinfect your water system:
- A garden hose that is long enough to reach from your water faucet to the well. This hose also needs to reach an area that is away from your well, septic system, landscaping, and bodies of water.
- Clean 5 gallon bucket.
- Plastic tarp.
- Protective goggles/face shield and rubber gloves.
- Five gallons of commercially bottled water.
- Chlorine test papers.
- Unopened, unscented household bleach with no additives that is less than six months old.
|STEP 1 - Isolate critical areas|
|Turn or push the bypass valves to the “bypass” or “out of service” position for all water treatment devices (water softeners, reverse osmosis systems, etc.) and appliances that cannot tolerate bleach. These may harbor organisms and need to be disinfected separately. Follow manufacturer’s instructions for disinfection procedures.
Remove all filters from devices and appliances. Bait tanks and livestock watering troughs may require special attention.
|STEP 2 - Electrical safety|
|Turn OFF the electrical power to the pump. If the circuit breaker box has a lockout hasp, use it to prevent the breaker from being accidentally turned ON.|
|STEP 3 - Open the well|
Open the well by:
Note: If the well is different from those described, contact Minnesota Department of Health (MDH) or an MDH licensed well contractor. You will find MDH contact information on the last page of this document.
|STEP 4 - Inspection|
|Inspect all well components by examining:
|STEP 5 - Mixing a bleach solution|
|Water chemistry and water system sizes vary. These differences will determine the amount of bleach solution that will be needed to properly disinfect your water system. You want between 50-200 parts per million (ppm) of bleach in the recirculating water (Step 7) for disinfecting your water system. Do not mix bleach solution that is greater than 200 ppm. A bleach solution with greater than 200 ppm of bleach will reduce the disinfection effectiveness.
It is recommended to start with:
The amount of water in a well is the total depth of the well minus the static water level. If the amount of water in the well is unknown, go to Minnesota Well Index or contact MDH. If unable to determine the amount of water in the well, use the total depth of the well instead.
This table’s bleach solution is good for disinfecting a well and the water system in an average home, including water pipes, water tanks, and water heater. Reduce the amount of bleach by 1 cup if only the well needs to be disinfected. You may need to increase the amount of bleach solution if:
|STEP 6 - Adding bleach solution to the well|
|STEP 7 - Recirculate chlorinated water|
|STEP 8 - Bring bleach solution to faucets|
|STEP 9 - Disinfection time|
|STEP 10 – Remove the chlorinated water|
|STEP 11 - Disinfecting water treatment systems and appliances|
|To disinfect water treatment systems and appliances, follow the manufacturer’s instructions for each water treatment device or appliance. If disinfection information is unavailable, contact your water treatment or appliance service provider. Bleach solutions may damage or improperly disinfect filters that are a part of a water treatment system or appliance.
|STEP 12 - Reconnect appliances, water softeners, and other treatment devices|
|Return bypass valves to ON position after following the manufacturer’s directions for disinfecting appliances and water treatment devices.
|STEP 13 – Test the water|
|After the bleach solution is removed from the water system, it is recommended that you take a water sample to make sure that the well water tests negative for total coliform before you use it for drinking or cooking. MDH recommends using an accredited laboratory to test your water. Contact an accredited laboratory to get sample containers and instructions, or ask your county environmental or public health services if they provide well water testing services.
Replace filters on all devices and appliances when MDH or an MDH certified laboratory confirms your water system is total coliform free.
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Total coliform may regrow in the water system. For this reason, it is important to retest your water between two to four weeks after disinfection. If total coliform is detected, repeat the disinfection procedure.
It is not unusual to disinfect a water system multiple times to eliminate total coliform if it has been growing in the system for a period of time. If disinfection attempts are unsuccessful, the well may need to be cleaned as well as disinfected. Contact a MDH licensed well contractor for further assistance.
For more information on your well and water system, see the “Well Owner’s Handbook (PDF).”
For additional information: Contacting the Well Management Section.
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Contact the MDH Well Management Section
651-201-4600 or 800-383-9808
Minnesota Department of Health