A rolled and grooved copper potable water piping system may be installed ___________________________.

The correct answer indicates that a rolled and grooved copper potable water piping system may be installed after the first valve downstream of the meter. This is in accordance with plumbing standards that ensure the integrity and safety of potable water systems.

When installing plumbing systems, it is crucial to maintain water quality and prevent contamination. The first valve downstream of the meter is critical because it is the point where the utility's responsibility typically ends, and the property owner's responsibility begins. Installing a rolled and grooved copper piping system in this location allows for the use of modern piping techniques while ensuring that the utilities’ drinking water standards are met.

By allowing the installation after the valve downstream of the meter, it ensures that any modifications or installations made will not compromise the integrity of the utility's water supply, which must remain uncontaminated. It also provides flexibility for repairs and expansions within the confines of the owner's water distribution system, as it can accommodate various fittings and configurations necessary for effective plumbing design.

Other options do not provide the same level of assurance regarding water safety and can lead to potential issues, such as contamination or pressure irregularities, which are critical considerations in plumbing code regulations.