To find a small degree of pollution in private wells on the first test is a common occurrence, which, in many cases, is easily remedied. Three typical occurrences are:

• The well may have been opened to clean it, and a disinfection treatment was not made on the system upon completion of the work.

• When a new pump or new pipe is installed, bacteria from the soil or contamination from other sources may get into the water system.

• Surface water may have flooded over the well cap or cover or otherwise seeped into the water system.

In any event, once contamination is found to exist in the water system, a disinfection treatment using liquid bleach should be done. After disinfection, allow enough time for the bleach to leave your system before taking another sample to test. In the meantime, until the test indicates a safe coliform bacteria level, continue to boil your drinking water for two minutes.


Remove the cap or cover from the well casing. Pour approximately 3 gallons* of liquid bleach directly down the casing. Connect a hose to a nearby spigot and run the hose down in the well casing, using the hose to recirculate water back into the well. Turn on water for one hour. This will thoroughly mix the bleach with the water standing in the well. Wash any foreign matter from the inside of the casing and the drop pipes. Take the hose out of the well casing after recirculating the water and put cap or cover back on. Before the next step disconnect or bypass any water systems that are in line. Next, run the treated water through all of the cold water pipes, discharging it from every spigot in the line for 5 minutes or until you smell chlorine. Shut the water off and let it stand overnight.

The next day, run the treated water through all of the cold water pipes, discharging it from every spigot in the line for 15 minutes. Then place a hose on an outside tap and allow it to discharge beyond the house. Use your own judgment discharging the water. It may depend on the condition of the pump, the flow rate, and water level in the well. We suggest ON for 1 hour, OFF for 2 hours. After all of the chlorinated water has been pumped out, wait two or three days before you have another sample tested. Do not take a sample for testing if the odor of chlorine is still present in the water.

* There are two rules of thumb in determining the amount of disinfectant to add. One calls for) gallon of bleach per 100 feet of well depth. The other calls for 1 cup of bleach per foot of actual water in the well. If you are unsure of either one of these, it is best to play it safe and use about 3 gallons of bleach.


The information and recommendations contained herein are, to the best of Pro-Spec's knowledge and belief, accurate and reliable. This document is offered in good faith. Pro-Spec does not warrant or guarantee accuracy, reliability, or completeness, It is the user's responsibility to satisfy himself as to the suitability and completeness of such information for his own particular use. We do not accept liability for any loss or damage that may occur from this information.