Should I test my private drinking well?

Residents who receive their drinking water through a municipality enjoy peace of mind knowing that their potable water undergoes routine bacteriological testing behind-the-scenes. But how do you know if water from your private well is safe and free of bacterial contaminants? Many residents with private wells are surprised to learn that they are responsible for testing their own well to ensure safety.

Importance of testing your well water

It is recommended to test your private drinking well for coliform bacteria on a yearly basis. Coliform bacteria are a group of bacteria used as “water quality indicators.” Since these bacteria are associated with harmful pathogens, their presence implies that the sample likely contains pathogen-carrying contamination. Escherichia coli (E. coli) is a species of coliform bacteria that is strongly associated with the feces of warm-blooded mammals. A positive E. coli test suggests that fecal contamination may have taken place. The presence of total coliform or E. coli indicates that the water is carrying contamination. This contamination can pose a serious health risk if ingested.

If you suspect that contamination has occurred and are waiting for test results,  avoid using your untreated well water for drinking, cooking, bathing, washing produce, or brushing your teeth. For these purposes use only water that has been brought to a rolling boil for a minimum of one minute and allowed to fully cool. Alternatively, store-bought water can be used for these purposes.

What to do after a positive bacteria test

If your sample tests positive for total coliform or E. coli, the lab may perform additional tests to confirm the initial findings. The lab will recommend collecting a second sample to verify the results of the first test. If the lab confirms the presence of total coliform or E. coli bacteria, it is necessary to disinfect and flush your well before returning to normal consumption.

A solution of water mixed with common unscented disinfecting bleach is sufficient to disinfect your well. Add the recommended volume of bleach from the chart below to 1 gallon of water to make your bleach solution. Remember to only use standard, unscented chlorine bleach. Do not use low-splash, scented or color-safe bleach.

Source: Florida Department of Health

How to disinfect your well and plumbing

After you make your bleach solution, follow these steps from the Florida Department of Health (FDOH):

  1. If you have a water softener or filter, disconnect the power to these appliances, and put them in “bypass” mode. Disconnect the power and close the supply to your hot water heater. Drain your hot water heater following manufacturer recommendations.
  2. In a clean bucket, mix the recommended amount of bleach from the above table into 1 gallon of water. Note that 1 cup equals 8 ounces, and 2 tablespoons equals 1/8 cup.
  3. Turn off the electric to your well pump. This may involve turning off the circuit breaker or unscrewing the fuse. Do not restore power until after you have added the chlorine solution to your well.
  4. Use a funnel to pour the bleach solution into the threaded opening of the well. Avoid spilling the chlorine solution on wire connections. Allow the chlorine to remain in the well for 30 minutes before flushing your system.
  5. Restore power to your pump.
  6. Open the water to one household plumbing fixture. Run the water until you smell bleach. Close the fixture. Repeat this step for all fixtures including both hot and cold fixtures, toilets, showers, baths, and outside faucets.
  7. Allow the chlorinated water to sit in the plumbing overnight or for a minimum of eight hours.
  8. Connect a garden hose to an outside faucet. Open the faucet and allow the water to drain onto the ground until you can no longer smell chlorine. Turn on one household fixture and allow the water to run until you can no longer smell chlorine. Repeat this process with each fixture.
  9. Follow the manufacturer’s instructions for disinfecting and reconnecting any filters or water softeners.
  10. Refill and start your water heater according to the manufacturer’s instructions.
  11. Have your water re-tested by an FDOH-certified laboratory before you resume consuming your water.

A big thank you to Florida Dept. of Health for collaborating with UF/IFAS Extension Sarasota County in providing this information.

Learn more


Florida Dept. of Health

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Posted: October 27, 2022

Category: Disaster Preparation, Home Management, Natural Resources, Water
Tags: Bleach, Coliform, Disinfectant, Drinking, E. Coli, Escherichia Coli, Pgm_Water, Potable, Test, Well

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