CSLB Class B General Contractor's License Practice Exam

By what measurement are plumbing waterline sizes typically calculated?

1. Cubic feet

2. Fixture units

3. Pound-force

4. Linear feet

The correct answer is: Fixture units

Plumbing waterline sizes are typically calculated using fixture units. Fixture units provide a standardized way to estimate the demand that various plumbing fixtures will place on a water supply system. This unit of measurement considers the type of fixtures, their usage patterns, and the expected peak demand, which allows plumbers and engineers to design a system that can adequately supply water without overloading the pipes. Using fixture units, plumbing professionals can determine the appropriate pipe sizes needed for different parts of a plumbing system, ensuring sufficient flow and pressure for the fixtures being served. This method is important for the efficient design and proper functioning of water supply systems in residential and commercial buildings. While the other measurements listed—cubic feet, pound-force, and linear feet—have relevance in different contexts, they do not specifically address the calculation of water line sizes in relation to fixture usage, which is the primary focus here. For instance, cubic feet might pertain to volume, pound-force to weight, and linear feet can refer to the length of pipe without addressing the functional aspect of varied fixture demands. Thus, fixture units stand out as the correct and most applicable choice for sizing plumbing waterlines.