Which factor distinguishes a Public Water System from a private system?

The distinguishing factor of a public water system is based on the number of people it serves continuously. A public water system is defined as one that serves 25 or more individuals year-round, which can include both residential and commercial users. This criterion is significant because it establishes a baseline for the scale and impact of the system on public health and safety. Public water systems are subject to more stringent regulations and monitoring than private systems because they provide water to a larger number of people, which raises the importance of maintaining safe and reliable water quality standards.

The other choices do not accurately define the distinction between public and private systems. For example, a public system being privately owned does not differentiate it on the basis of service, as ownership type is separate from the classification of users served. The focus on agricultural use or transient users does not encompass the general scope of public water systems, which are designed to serve a consistent population rather than a temporary or specialized group. Thus, the correct answer emphasizes the requirement for year-round service to a substantial number of individuals, ensuring that public systems meet necessary health and regulatory standards.