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What are coliforms?

Coliforms are a broad class of bacteria found in our environment, including the feces of man and other warm-blooded animals. The presence of coliform bacteria in drinking water may indicate a possible presence of harmful, disease-causing organisms.

Why use coliforms to indicate water quality?

Drinking water must be free of disease-causing organisms called pathogens. Pathogens can be viruses, protozoa or bacteria. Waterborne pathogens cause diseases such as hepatitis, giardiasis, and dysentery. To actually test water for specific harmful viruses, protozoa and bacteria is very time consuming and expensive. In addition, not all water laboratories are equipped and approved to do the testing required. Therefore, testing water for specific organisms is limited to investigating specific waterborne disease outbreaks. Coliform bacteria are used as water quality indicators for two main reasons:
  • Coliforms may be associated with the sources of pathogens contaminating water.
  • The analysis of drinking water for coliforms is relatively simple, economical and efficient.

The presence of coliforms in drinking water indicates possible contamination and potential health risk.

Sample submission

Sample containers may be picked up in all Health District offices during regular business hours. Request a bacteriological or Coliform analysis. Samples must be received and setup within 30 hours of sample collection and kept cool during transit.

When collecting samples take care not to contaminate the sample container. Go to a tap where you draw your drinking water and remove aerators, screens, or other devices. Turn the water on to a moderate flow and let run for a minimum of 3 minutes. Without altering the flow, collect your sample. Leave a inch air space at the top of the bottle. Cap the bottle and return it to the laboratory as soon as possible.

What to do if coliforms are found in your drinking water:

Drinking water analyzed for coliforms will be reported as SATISFACTORY (coliforms absent) or UNSATISFACTORY (coliforms present). If your drinking water tested unsatisfactory, you should have received information on how to disinfect your well. If you did not receive this information, contact the laboratory at 460 4206 or the Environmental Health Division at 460 4205. The information can then be mailed to you or instructions can be given over the phone.

If your drinking water tested UNSATISFACTORY, it may be contaminated with disease-causing organisms. It is important that you do not drink the water and that appropriate action is taken until the problem is corrected. One option is to obtain bottled water from a safe source on a temporary basis. Another option is to boil the water vigorously for 3-5 minutes to render it safe from bacterial contamination.

If coliforms are not present in your drinking water samples (you received a SATISFACTORY result), it indicates that your well is probably free of disease-causing organisms at the time of the sample. Be sure to have your water tested annually; more often if you notice a change in taste or odor of the water, or if there are changes in the environment of your well control area (such as flooding).

Protecting your well from potential contamination is important.

It is recommended that your well:

  • be separated from sources of contamination such as surface drainage and barnyard runoff,
  • is not located within 100 feet of a septic system where an opportunity may exist for wastes to enter the well,
  • has a sanitary seal specifically designed for the top of the well casing. This seal must be correctly positioned, with all openings properly sealed to disallow the entrance of any potential contaminant into the well casing and ultimately into the water source.
  • In addition, inspect surrounding areas within a 100-foot radius of the well for sources of pollution such as garbage, animal pens, barns and agricultural areas (including your home garden).

For more information and/or assistance, contact the Environmental Health Division at 460 4205 or the BFHD Laboratory at 460 4206.
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Benton Franklin Health District
7102 W Okanogan Pl
Kennewick WA
(509) 460 4200
412 W Clark
Pasco WA
(509) 547-9737

Emergency Contact Information

Personal Emergency for Medical, Police, Fire, or Other: 911
Washington Poison Center: 1 (800) 222-1222 (www.wapc.org)
Washington Community Resource Information: 211 (www.win211.org)
BFHD Public Health Emergency/Imminent Health Hazard After-Hours Reporting: 509-543-3851
The public can reference BFHD policies available in Kennewick office.
BFHD Privacy Statement:English / Spanish
Copies of the annual report available at all BFHD offices.
State and County Resources
Rules and Regulations Administered by or Governing the Benton-Franklin Health District
WAC's - RCW's
Community Health Status Indicators
Reportable Conditions
Contact: info(at)bfhd.wa.gov                                                                                                                             Employees