A service sink with a three inch trap standard would have a fixture unit rating of ________________________.

The fixture unit rating for a service sink with a three-inch trap is standardly assigned a value of three fixture units according to plumbing codes, including the Omaha Plumbing Code. Fixture units are a way to quantify the load that a plumbing fixture contributes to the overall drainage system.

In this context, a service sink is typically used for cleaning and services that require larger volumes of water, which is why it has a higher rating compared to other smaller fixtures. The three-inch trap allows for greater flow and capacity to handle the waste, aligning with the rating of three fixture units. This rating plays a crucial role in sizing the drainage and venting systems appropriately to ensure they can handle the expected flow rates without causing backups or other plumbing issues.

The other choices do not align with the established standards for a service sink with a three-inch trap, as they reflect either under or overestimations of the fixture units based on typical plumbing codes. Thus, the assignment of three fixture units accurately represents the service sink's capacity in the plumbing system.