NEWSplash!: Contamination of Wells Higher Than Usual

Contamination of Wells Higher Than Usual
August 30, 2000 – Newsletter

The year 2000 has seen a significant rise in well water contamination rates. A 70% increase in the failure rate for coliform bacteria was noted for this year compared with 1999. The samples of fresh water tested by Suburban Water Testing Laboratories, Inc. during the period of January to July of 1999 showed the presence of coliform in 10.2% of the samples. For the same period in the year 2000 this figure jumped to 17.6 %. The actual incidence of coliform positive wells is somewhat higher as many of the water supplies tested are already treating the water to eliminate coliform.

Differences in rainfall, water usage patterns and increased development of land can all contribute to higher levels of coliform. Increased rainfall causes higher water table levels which can more easily contact sources of pollution such as septic system absorption areas. Excessive rain may cause flooding around well casings and allow surface water to rapidly enter local sources of drinking water. Drought conditions or heavy demands on local wells can cause the water table to lower and may shift underground water flows so that pollution suddenly appears in a water supply that previously tested within limits.

The responsibility for testing of private wells rests with the well owner. Public water supplies test the drinking water a minimum of once a quarter. Larger municipal supplies may perform coliform tests numerous times each day. Private wells should be tested at least once a year. Testing every nine months is a better plan as it results in the water eventually being tested in all four seasons and helps to identify wells that have seasonal contamination.

Time easily slips by so that before you realize it a number of years have passed since the well water was tested. Diarrhea, abdominal pains or other sicknesses contracted from the water may be attributed to the flu, the bug that’s going around or some other source unrelated to the water supply. Many cases of water borne illness are never traced to their real source, namely, the drinking water. Many laboratories can arrange for reminder cards or calls so that water testing is done on a regular basis and is not overlooked.

Periodic inspection of the well head by a laboratory technician, well driller or plumber can help avoid contamination problems around the well. Loose fitting well covers can allow insects, small rodents or other creatures access to a water supply. Earwigs and various species of ants are often found inside a well. At times these construct large nests inside a well casing. When the insects fall down inside the casing they often are unable to crawl back up to the surface. These die and decay in the well, and in some cases the strainers at the faucets may become clogged with insect parts.

Tight fitting well seals with filtered air vents are available to help remedy this problem. Unfortunately, these are seldom installed on residential wells unless specifically requested. An inexpensive handyman alternative is to cut a section of plastic screen material such as is used in doors and windows and carefully place it over the top of the well casing. Enough screen material should be used so that it extends downward over the well casing several inches. A large screw clamp can be used to hold the screen tight against the well casing. The loose fitting well cap can then be placed over the clamped on screening. For more information see

Other practical steps to protect a well include: Use weed killers and pesticides sparingly according to the label directions and avoid use near the well head. Keep stored chemicals and solvents away from a well and never dispose of chemicals, paints, oils, fuels or solvents on or under the ground.

In some cases a well head may not protrude above the surface of the ground. Such wells should have the casing extended above the ground and be fitted with a tight fitting well seal or have screening installed as mentioned above.

While protecting your well does not completely eliminate the potential for contamination, an ounce of prevention is certainly worth a pound of cure. Treatment devices are available for most water contamination problems where the source of the contamination cannot be eliminated. A source of water treatment equipment
dealers can be found on the Water Quality Association web site at