Group B Public Water Systems - Information

Information for Consumers, Owners, and Operators

There are three main classifications of water systems in Washington:

  • Private (also called “individual wells”)
  • Group B public water systems
  • Group A public water systems

Owners of private water systems typically have minimal requirements that apply to their own water system. Local governments (such as the county) usually require a well test for new construction, and the results provide the “proof of adequate water supply.” Once homes are built, there are usually no regulations that apply to owners of private wells.

Group B systems serve more than a single home. They serve fewer than 15 service connections and fewer than 25 people per day. New or expanding Group B systems must be approved by us or a local health jurisdiction. If you have questions about the requirements for approval of a Group B system, visit our design webpage that has specific information about those requirements.

Group A Public Water Systems have comprehensive monitoring requirements under the Safe Drinking Water Act.

Even though there may not be specific monitoring, operations and maintenance requirements, we've created a number of helpful tips for owners and operators of both private and Group B systems. For more information, visit our operations and maintenance webpage.

Testing for coliform bacteria and nitrate

If you are a Group B water system consumer, you should regularly communicate with your system's owner and operator about the system. Although not required, the best way to know if your drinking water is safe is to test the water quality of the system. We have tips on how to monitor for contaminants that are commonly tested, mainly coliform bacteria and nitrate. When water quality monitoring shows a contamination problem, the system owner or operator has a responsibility to notify you of the problem.

For a list of certified labs, visit the state Department of Ecology. Under "Location," select your state, city, and county. Scroll down and click on "Show results." Click on the name of a lab to see the tests it performs. Call the lab to make sure it's accredited to analyze for coliform bacteria and nitrate.

Concerns about arsenic

The arsenic drinking water standard for Group B systems of 10 parts per billion applies to new or expanding Group B systems approved after January 1, 2014.

If your system was approved before January 1, 2014, your drinking water may exceed the 10 parts per billion standard. Your system is not out of compliance, but you may want to take extra precautions to protect your health. Visit our Group B arsenic webpage for more information.

Go back to the Group B Main Page.