Emergency Procedures for Disinfecting a Flooded Well

John Branch, Bankston, Jr., Joseph D.

When flooding occurs, the concern for the safety of the well water arises due to the possibility of contaminated flood waters following a direct path to either water in the wells piping or to water in the aquifer immediately surrounding the well. This path could be caused by a leak in the piping system (including the pump) connected to the well or by an improperly sealed well that provides a path from the surface to the aquifer in which the well is operating. This problem could also occur due to penetration into the aquifer, perhaps by an old, unsealed well. Most often, the contamination of concern is bacteria. If the well is properly sealed in accordance with state standards, there is no leak in the piping system and there is no penetration into the aquifer in the vicinity of your well, the water should not have incurred a safety problem due to the flood. Note: if you have to prime the pump, be sure to sanitize the area of the pump and/or pipe that you will open to prime the pump.

However, if you are in doubt as to the safety of the water you could either have the water tested (see below) or disinfect or have the well disinfected. Note the disinfecting procedure described here is intended for bacterial disinfection and would not be expected to be suitable for chemical contamination.

Disinfecting a well can sometimes be done by the well owner; however, for some wells it can be difficult to get the disinfectant into the well or other parts of the system that need disinfecting. Hiring a well contractor to disinfect the well for you is recommended. If professional help is not available for cleaning the well, follow these procedures:

Caution: When you use the pump to flush the dirty water from the well, provide an outlet for the water near the pump so the dirty water doesn’t run through the home’s interior plumbing.

  1. Pump the well to reduce the cloudiness and contaminant levels in the water. Provide an outlet near the pump for the water so it doesn’t run through the home’s interior plumbing.
  2. Turn off the pump and leave it off until you are ready to remove the highly chlorinated water. Pour 4 gallons of chlorine bleach solution into the well (1 gallon of bleach with 3 gallons of clean water). Do not use bleach substitutes. (You can make your own chlorine bleach solution by adding ½ cup of chlorine tablets to 4 gallons of water.) Wait at least four hours, to allow the chlorine to act on contaminants in the well itself. Since the chlorine may free contaminating particles from the walls of the well and plumbing, pump the first batch of chlorinated water out through the faucet nearest the well. Chlorinate again.
  3. Caution: Before drawing freshly chlorinated well water into the home, protect water softeners, water filters, septic systems and other devices that may be affected by too much water, sediment or excess chlorine in the water. If you’re uncertain about how to protect a device, check the owner’s manual or contact the manufacturer. Begin flushing the interior plumbing by opening the cold water faucet closest to the pump. Pump the water until the water at the faucet smells of chlorine. If this does not occur, shut off the pump and repeat steps 2 and 3 until the odor is detected at the faucet.
  4. Shut off that faucet and move to the next cold water faucet, running the water till you smell chlorine coming out at that faucet. Continue until all faucets have been sampled – outside and inside the house. Flush the hot water lines last; this will also flush the hot water heater.
  5. With all faucets closed, let chlorinated water stand in the well and in pipes for 24 hours.
  6. Run the water from all the faucets – hot and cold - until the chlorine smell disappears.

These steps will usually result in adequate reduction of bacterial contamination, but some conditions could interfere with the disinfecting. It is best to test the water and not use it for drinking until test results show it to be free of bacterial contamination. Testing again after 10 days is recommended. You can discuss the final lab results with your lab or local parish health unit.

Testing for Bacteria

The parish sanitarian, Louisiana Department of Health and Hospitals, can test your water for bacterial contamination. For a fee of $75, trained sanitarians collect the water sample from your home and deliver it to a state laboratory, where the sample is analyzed for coliform bacteria ONLY. The test results are sent to the well owner. If the test is positive for coliform bacteria, the sanitarian will contact you with suggestions for correcting the problem. The well should be resampled until a negative test result is obtained. Any necessary resampling is included in the initial fee.

For more detailed information on how to protect your well from biological and chemical contamination, read the AgCenter Farm*A*Syst well protection fact sheet.

3/29/2005 11:15:45 PM
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