When a lab report on the well water sample you submitted shows that it has exceeded the allowable bacterial standards for drinking water, please follow the procedures outlined below to try to eliminate the source of contamination.

For drilled wells:

• Examine the equipment for breaks, leaks, rust, and disrepair. Verify that the top of the drilled well has a sanitary seal (a rubber gasket held in place by bolts through the top of the well). The bolts, as they are tightened, compresses this rubber gasket to form a tight seal to the sides of the casing. Check where the electrical wires go through the top of the well casing, and see if there are any gaps between the wires and the casing openings. The area around the wires should be sealed with putty, silicone caulk, or other suitable material. This prevents the entrance of insects, small animals, and dirt into the casing. The well casing vent (usually shaped like a candy cane) should be covered at the end of the vent with a fine mesh screen which also prevents the entrance of insects.
• Examine the reservoir for algae, mold, slugs, and small animals. You may want to drain the reservoir and scrub the inside with a solution of 1 tablespoon household bleach in 1 gallon of water.
• CAUTION: Make sure the area is well ventilated and do not use ammonia at all. Afterwards, make sure the lid is sealed with a gasket and that the overflow pipe is screened to prevent insects, rodents, etc. from getting into the reservoir. You should have a closed system, which means that there is no opening, no matter how small, between the water from the well and the faucets (except for properly screened vent and overflow pipe).
• Disinfect the system. Please follow the instructions provided in the fact sheet "Disinfection of Private Wells." Follow the steps outlined for drilled wells.
• Approximately 5 days after disinfection, you can take another water sample. Take it from a faucet as far away from the well as possible. If this sample is unsatisfactory, you may contact the public health department for advice or call a licensed well driller or water system designer.

For dug wells:

• Dug wells, because they are shallow and the water is not from a protected aquifer, are usually easily contaminated and not easily decontaminated. Please follow the instructions provided in the fact sheet "Disinfection of Private Wells." Follow the steps outlined for drilled wells.
• You need to make sure that the source is as protected as possible. The inside of the well should be lined with concrete tile or other durable material, and a protective cover should be placed over it. The cover should have a built-up edge under it, to prevent water and dirt from running into the well. It should a have a gasket to seal the opening. Concrete (with handles) is the preferred material for the cover.
• The area around the well should be free from sources of contamination (such as a drainfield, septic tank, pasture, barn, garage) for 200 feet in any direction.
• If your efforts at decontamination have no effect, you should consider connecting to another, approved source of water, drilling a new well, or adding a chlorinator.