Group B Water Systems

Group B Water Systems

Group B Water System Emergencies webpage.

Group B public water systems serve fewer than 15 connections and fewer than 25 people per day. The Office of Drinking Water and local health jurisdictions regulate Group B systems in our state.

Group B systems are regulated under chapter 246-291 of the Washington Administrative Code. A new Group B rule was adopted by the State Board of Health in October 2012 and went into effect January 1, 2014. You can find the New Group B Rule 331-071 (PDF) and a Summary of Final Rule Changes (PDF) on our Drinking Water Rules webpage.

Rule Effective January 2014

All Group B systems are subject to the rule beginning in 2014. In general, the rule:

  • Requires more stringent design standards for new and expanding systems.
  • Eliminates all requirements for most one connection and two connection Group B systems.
  • Doesn't require routine ongoing monitoring.

If your complete design application is received after January 1, 2014, refer to the New Group B Rule 331-071 (PDF) and the Group B Water System Design Guidelines 331-467 (PDF) and Group B Design workbook 331-468 (Word).

Regulation of Group B Systems

The Group B rule allows local health jurisdictions (LHJs) to adopt their own regulations, as long as the locally adopted requirements are not less stringent than the state rule. Many LHJs adopt rules for Group B systems that include additional requirements. For example, some local regulations may include requirements for Group B systems with one or two connections, and others include routine ongoing water quality monitoring and reporting.

This map shows local health involvement with the Group B program (PDF). LHJs can adopt a local ordinance, have delegated responsibility through a Joint Plan of Responsibility (JPR), or have no involvement with Group B water systems. If your water system is in a county without LHJ involvement, the following is a summary of our water quality monitoring recommendations for Group B water systems. 

  • Coliform Bacteria. Start sampling for coliform bacteria by following the schedule in Section 33 on the second page of your Water Facilities Inventory (WFI) form. You can also find it on your Water Quality Monitoring Schedule (WQMS). The coliform schedule indicates the minimum number of coliform samples required from your water system each month (WAC 246-290-300). For questions, contact your regional office. 
  • Nitrate Monitoring. Check the nitrate monitoring schedule in Section 34 on the second page of your WFI form. You may also find it on your Water Quality Monitoring Schedule (WQMS). For questions, contact your regional office. 
  • Accredited Drinking Water Laboratory. All water quality samples must be analyzed at an accredited drinking water laboratory. To ensure your system receives proper credit for samples, remember to include your public water system identification number, which is a combination of the first five digits and letters on all submitted samples. Be sure to fill out each section of the chain of custody lab analysis form. Incomplete or unreadable lab analysis forms may result in the need to re-sample. Lab personnel can tell you how to collect samples for different tests. To find a list of accredited labs in your area visit the Department of Ecology lab search website. For questions, contact our Headquarters office.

Additional Information

If you are planning to create a new Group B system or expand your existing Group B system, visit our Group B Design webpage that describes system requirements. The webpage also has links to design guidelines, forms, templates, and includes other helpful information you will need to be successful in your project.

If you are an owner or operator of an existing Group B system, visit our Operations and Maintenance webpage. This page links to technical assistance and forms you may need.

For consumers who receive water from a Group B system, go to our general information about small water systems webpage, with links to information about steps you can take to keep yourself and your household healthy.

For a list of certified labs, visit the state Department of Ecology lab search webpage. 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 the drinking water parameter you want analyzed.

For a list of additional resources for Group B water system, visit our Group B Resources webpage.

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