According to the Massachusetts Plumbing Code, how should potable water be supplied to a building?

The correct choice reflects the Massachusetts Plumbing Code's requirements for ensuring public health and safety regarding potable water supply. The code mandates that potable water must come from either an approved public water supply or a safe, regulated private source. This requirement is crucial to guarantee the quality and safety of the drinking water provided to buildings, thereby preventing contamination and protecting public health.

Using a public water supply ensures that the water has undergone necessary testing and treatment to meet health standards. In situations where a public supply is not available, an approved private source, such as a well that has been tested and deemed safe, can serve as an alternative. This option allows flexibility for rural or less populated areas where public systems are not accessible while still ensuring that the water supplied is safe for consumption.

Other alternatives such as a non-potable source do not meet health standards required for drinking water, while rainwater harvesting systems, although beneficial for certain uses, may require additional treatment to ensure safety before being considered potable. Therefore, the emphasis on approved sources in the Massachusetts Plumbing Code ensures that all water supply meets health and safety standards for end-users.