For a water closet using more than 1.6 GPF, which of the following correctly describes the trap and branch sizes?

The selected answer indicates that a water closet using more than 1.6 gallons per flush (GPF) requires a 3-inch trap and either a 3-inch or 4-inch branch. This is correctly aligned with plumbing code standards, which specify that higher flow toilets need larger plumbing to effectively handle the increased volume of waste and water.

Using a 3-inch trap is critical for ensuring adequate drainage capacity and preventing blockages. Additionally, having the option of a 4-inch branch enhances the system's ability to allow for optimal flow through the plumbing infrastructure as it connects to the greater drainage system. Larger pipe sizes reduce the risk of clogs and allow for proper venting, thus promoting a functional and efficient waste removal process.

In contrast, other options might suggest smaller dimensions that could lead to insufficient waste flow, which is not suitable for fixtures that are designed to use more water. This is why the dimensions of the trap and branch must adhere to the plumbing code to maintain functionality and compliance with regulations.