How does the code address water efficiency in residential construction?

The correct choice highlights that the code establishes standards for plumbing fixtures to encourage water conservation in residential construction. This is important as plumbing fixtures, such as faucets, toilets, and showerheads, account for a significant portion of water usage in homes. By setting specific performance criteria for these fixtures, the code aims to reduce water consumption without compromising functionality or health standards.

Implementing these standards helps promote efficient water use, ultimately leading to lower water bills for homeowners and a reduced environmental impact. The emphasis on efficiency aligns with broader sustainability goals and helps ensure that water resources are used wisely, especially in regions where water scarcity may be a concern.

In contrast, while other options involve water management strategies, they may not necessarily be part of the core code requirements. For example, the use of recycled materials is oriented toward sustainable building practices rather than direct water efficiency. Similarly, rainwater harvesting systems, though beneficial for water reuse, are not universally mandated in residential building codes, and enforcement of penalties for excessive water usage does not directly address the construction or efficiency of plumbing fixtures.