Private and public systems

The following is an excerpt from the Washington Administrative Code (WAC) discussing differences between Group A and Group B public water systems and categorizing different types of Group A public water systems.

Excerpts from WAC 246-290-020:

Public water system shall mean any system, excluding a system serving only one single-family residence and a system with four or fewer connections all of which serve residences on the same farm, providing piped water for human consumption, including any:

1. Collection, treatment, storage, or distribution facilities under control of the purveyor and used primarily in connection with such system; and
2. Collection or pretreatment storage facilities not under control of the purveyor primarily used in connection with such system.

A Group A system shall be defined as a public water system:

1. With fifteen or more service connections, regardless of the number of people; or
2. Serving an average of twenty-five or more people per day for sixty or more days within a calendar year, regardless of the number of service connections.

Group A water systems are further defined as community and noncommunity water systems.

1. Community water system means any Group A water system:
   1. With fifteen or more service connections used by residents for one hundred eighty or more days within a calendar year, regardless of the number of people; or
   2. Regularly serving twenty-five or more residents for one hundred eighty or more days within the calendar year, regardless of the number of service connections.

Examples of a community water system might include a municipality, subdivision, mobile home park, apartment complex, college with dormitories, nursing home, or prison.

2. Noncommunity water system means a Group A water system which is not a community water system. Noncommunity water systems are further defined as:
   1. Nontransient (NTNC) water system which regularly serves twenty-five or more of the same nonresidents for one hundred eighty or more days within a calendar year.

      Examples of a NTNC water system might include a school, day care center, or a business, factory, motel, or restaurant with twenty-five or more employees on-site.

   2. Transient (TNC) water system which:
      1. Has fifteen or more service connections used less than one hundred eighty days within a calendar year; or
      2. Serves twenty-five or more different nonresidents for sixty or more days within a calendar year; or
      3. Serves twenty-five or more of the same nonresidents for sixty or more days, but less than one hundred eighty days within a calendar year; or
      4. Serves twenty-five or more residents for sixty or more days, but less than one hundred eighty days within a calendar year.

Examples of a TNC water system might include a restaurant, tavern, motel, campground, state or county park, an RV park, vacation cottages, highway rest area, or church.

3. A Group B water system is a public water system which does not meet the definition of a Group A water system.