Private & Non-Community Water Supplies

What Every Homeowner and Non-Community Operator Should Know About Their Water Supply

Bacteria in Water

Baceria and paasites which cause illness can get into a well from the materials and tools used in construction or from septic system failures near the well. These bacteria and parasites must be destroyed.

Every new, modified, or reconstructed water well, including pumps and all pumping equipment, should be disinfected before being used and each time it is opened for maintenance or repair. The disinecting must be done by the well and pump contractor after the well and pump installation is completed. Water supplies should be free of bacteria after the system has been completely disinfected.

Testing for Coliform

The Department recommends that all new wells or wells which are repaired should be tested in order to assure a safe water supply. Bottles for testing your water are available from the Department Laboratories, Regional Offices, and many local health departments.

Testing for coliform bacteria provides information on the probability of contamination of the water supply by infectious organisms, but it is not a direct measure of pathogenic bacteria. Specific disease-producing organisms present in water are not easily identified, and testing for these organisms in the laboratory is complex and time-consuming. It has been necessary to develop tests which indicate the relative degree of contamination in terms of an easily defined quantity. Coliform bacteria can be easily tested for in the laboratory. Coliform bacteria are used as the official indicator of the bacteriological quality of the water.

Some members of the coliform indicator group occur normally in the intestines of humans as well as other warm-blooded animals, and are discharged in great numbers in human and animal wastes. Other members occur naturally in surface water of varyingquality and in top soil. A positive analysis for coliforms indicates that the sample may have been contaminated by surface washings or fecal material. This may suggest that the water supply may not be properly constructed or protected from sources of bacteriological organisms outside the supply. Negative results indicate there was no contamination at the time of sampling.


A new water supply should be tested for nitrates. Nitrate levels above 10 mg/l as nitrogen may cause illness in infants six months of age or younger. Nitrates found in ground water are usually produced by agricultural fertilizers or livestock wastes.

Sample Collection

All bacteriological water sample bottles are sterilized prior to distribution. Once sterilized, the bottles are considered usable unless they are opened.

Select the location at which the water sample will be taken. It is usually desirable to use a sampling point as close as possible to the water supply source. Samples should not be collectd from garden hoses, or dirty faucets or swing-type faucets where foreign material may contaminate the sample. Faucets screens or aerators should be removed prior to the sampling.

Allow the water to run full flow from the sampling point for several minutes before collecting the sample. Let the water run until the pump starts and pumps for several minutes. This will allow for sampling of water directly from the ground supply, rather than water that has been in storage for a period of time.

Before taking the sample, adjust the tap to proide a stream of water approximately the size of a pencil. Remove the cap from the sterile bottle and take the sample immediately. Do not rinse out the bottle. Do not touch the rim of the bottle or the inside of the cap with your fingers or with the spout of the sampling point. Fill the water sample to the bottom of the neck, leaving an air space, and immediately replace the cap.

Return the water sample to be protective packing provided and place the bottle in its box. The protective packing will help prevent breakage during transportation.

Complete the report form. It is particularly important that the date of collection, sampling point, and return address be completed accurately. After completing the report form, place it in the box with the water sample bottle. Attach the mailing label and the required postage.

Mail the water sample as soon as possible, as the time lapse between sample collection and receipt of the sample by the laboratory is critical. Any sample received after more than 48 hours after collection will be discarded as being too old for testing. Samples should reach the laboratory no later than Thursday of any week.

Water Sample Results

The water sample testing results are sent to our Regional offices for interpretation and mailing to the homeowner.

When a positive sample has been received, the following procedures are recommended:

  • The well should be resampled immediately to see if further testing shows the presence of coliforms. This will help to eliminate the possibility of contamination of the sample itself due to improper collection techniques, a contaminated sample bottle, or the incidental contamination of pump or plumbing fitings.

If the resample is not satisfactory, the Department should be contacted for consultation. The water should not be used for drinking, culinary, or equivalent purposes until a satisfactory analysis has been obtained unless brought to a rolling boil for at least three minutes. Please note that boiling will not eliminate a high nitrate concentration; and, in fact, will increase concentration.

If the successive samples taken after disinfection indicate positie coliform counts, additional discretion is recommended. Sometimes it takes several disinfection attempts before bacteriologically safe water samples are obtained.

If the resample is negative for coliforms, and the nitrate concentration is less than 10 mg/l as nitrogen, then the water supply may be considered safe for drinking.

Illinois Department of Public Health Laboratories

Bottles for water sampling may be obtained from one of the following IDPH laboratories:

Chicago Laboratory
2121 West Taylor
Chicago, IL 60612
(312) 793-4760
Carbondale Laboratory
Chauauqua & Oakland Streets
PO Box 2797
Carbondale, IL 62901
(618) 457-5131
Springfield Laborator
825 N. Rutledge St.
Springfield, IL 62794
(217) 782-6562

Questions may be directed to your local health department, or to:

Illinois Department of Public Health
525 West Jefferson
Springfield, IL 62761
Division of Environmental Health
(217) 782-5830