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Coliform Bacteria


What Are Coliform Bacteria?


Coliform bacteria are common germs found in the environment. They can enter drinking water through septic systems, surface water, or human and animal waste. While many types are harmless, some can cause illness.


Types of Coliform Bacteria


There are three main types of coliform bacteria that may be found in drinking water:

How Can I Know if My Water has Coliform Bacteria?


If You Use a Private Well

Testing is the only way to know if coliform bacteria are present in your well water. 

We recommend testing your water at least once a year, and

  • After flooding
  • After well repairs
  • After a loss of water pressure from your well
  • If you notice changes in your water’s taste, color, or smell

Contact a certified drinking water testing lab to get a test kit, and follow the test kit or coliform sampling instructions to help ensure accurate results. Improper sampling can cause bacteria to appear in the results even when your water is not contaminated. 


If You Use a Public Water System:

Public water systems are required to regularly test for coliform bacteria and notify customers if a problem is found. If you have concerns about your water quality, contact your water system or review your system’s water quality report.


Interpreting Your Test Results


Use the examples below to understand what your results mean and what actions may be recommended.

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Contact Us

  1. Yakima Health District

  2. 1210 Ahtanum Ridge Drive

  3. Yakima, WA 98903

  4. (509) 575-4040

    Monday, Wednesday-Friday: 8:30am-4:30pm

    Tuesday: 9:30am-4:30pm


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