Which of the following is the correct waste fixture unit rating for a typical sink in a residence?

The waste fixture unit rating for a typical sink in a residence is assigned based on the expected drainage load that the fixture contributes to the plumbing system. This rating helps in sizing the drainage system correctly to ensure efficient wastewater flow and prevent clogging.

A typical sink, such as a kitchen or bathroom sink, is generally rated at 2 fixture units because it conveys a moderate volume of wastewater. This rating takes into account factors such as the frequency of use and typical discharge rates. The rating system allows plumbing designers to use a standardized method for calculating total demand in a drainage system, facilitating proper sizing of waste pipes and ensuring that the plumbing system can handle the expected load without issues.

Understanding the purposes of the other choices helps clarify why the correct answer is 2. Ratings like 1, 4, or 6 might correspond to different fixtures or installations, but they do not reflect the average load contribution of a residential sink. For example, a fixture rated at 1 might be for a very low-use fixture, while 4 or 6 would be more suitable for larger or more intensive use fixtures, such as showers or multiple bathroom sinks in a series.