What is a Public Water System?

A public water system is defined as any publicly or privately-owned system of pipes or other constructed conveyances, structures and facilities through which water is obtained for or sold, furnished or distributed to the public for human consumption, if such system has at least 15 service connections or serves at least 25 individuals daily at least 60 days out of the year or bottles water for sale. The term "public water system" shall include any collection, treatment, storage or distribution pipes or other constructed conveyances, structures or facilities under the control of the supplier of water and used primarily in connection with such a system, and any collection or pretreatment storage facilities not under that control that are used primarily in connection with such a system. (From the State of Maine Rules Relating to Drinking Water)

This definition means that if your establishment serves water from your own source (i.e., a well or surface water intake) to 25 or more people per day, or have 15 or more service connections, and operate for 60 or more days per year, you are operating a public water system. There are three types of public water systems and each is regulated differently. The three types are:

Community Public Water Systems

A public water system that serves at least fifteen service connections used by year-round residents or regularly serves at least 25 year-round residents is considered a Community public water system. (Year-round is defined as a permanent residence greater than six months.) Examples include water utilities, mobile home parks, apartment buildings, nursing homes, etc.

Click here for information about Manufactured Housing Communities (PDF) (mobile home parks, etc.)

Non-Transient, Non-Community Public Water Systems

A Non-Transient, Non-community (NTNC) public water system serves at least 25 of the same persons for six months or more per year. Examples include schools, office buildings, factories, etc.

Transient Public Water Systems

Transient public water systems are non-community systems that serve at least 25 persons, but not necessarily the same persons, for at least 60 days per year. Examples include restaurants, camps and campgrounds, motels and hotels, golf courses, etc.

Guidebook for Transient Public Water Systems (PDF)

Additional Resources

• Policy for Determining Classification and Overall Population of Public Water Systems (PDF)
• Policy for Estimating the Population of a Public Water System (PDF)
• New Well/New Source Approval
• Water Systems by County (PDF)
• Public Water System Mapping
• Municipal Water Systems (Public Water Utilities)
• Private Wells (Environmental and Occupational Health Program)

Updated 8/19/2024